Hi Anton, 

I have a stable reproducer. I released the same host and deployed it again with the same deployment options, and the issue happened again.

regiond: Lots of 204 NO_CONTENT log and https://bugs.launchpad.net/maas/+bug/2053042
```
2024-02-13 15:36:13 regiond: [info] 127.0.0.1 POST /MAAS/metadata/status/4nem8e HTTP/1.1 --> 204 NO_CONTENT (referrer: -; agent: python-requests/2.22.0)
2024-02-13 15:36:13 regiond: [info] 127.0.0.1 POST /MAAS/metadata/status/4nem8e HTTP/1.1 --> 204 NO_CONTENT (referrer: -; agent: python-requests/2.22.0)
2024-02-13 15:36:13 regiond: [info] 127.0.0.1 POST /MAAS/metadata/status/4nem8e HTTP/1.1 --> 204 NO_CONTENT (referrer: -; agent: python-requests/2.22.0)
2024-02-13 15:36:14 metadataserver: [info] No user data registered for node named perlman
2024-02-13 15:36:14 regiond: [info] 127.0.0.1 GET /MAAS/metadata/2012-03-01/user-data HTTP/1.1 --> 404 NOT_FOUND (referrer: -; agent: python-requests/2.22.0)
2024-02-13 15:36:14 regiond: [info] 127.0.0.1 POST /MAAS/metadata/status/4nem8e HTTP/1.1 --> 204 NO_CONTENT (referrer: -; agent: python-requests/2.22.0)
2024-02-13 15:36:15 regiond: [info] 127.0.0.1 POST /MAAS/metadata/status/4nem8e HTTP/1.1 --> 204 NO_CONTENT (referrer: -; agent: python-requests/2.22.0)
2024-02-13 15:36:15 regiond: [info] 127.0.0.1 POST /MAAS/metadata/status/4nem8e HTTP/1.1 --> 204 NO_CONTENT (referrer: -; agent: python-requests/2.22.0)
```

```
2024-02-13 15:36:57 regiond: [info] 127.0.0.1 GET /MAAS/metadata/2012-03-01/maas-scripts HTTP/1.1 --> 204 NO_CONTENT (referrer: -; agent: Python-urllib/3.8)
2024-02-13 15:36:57 provisioningserver.rpc.common: [critical] Unhandled failure dispatching AMP command. This is probably a bug. Please ensure that this error is handled within application code or declared in the signature of the b'ReportNeighbours' command. [maas:pid=320095:cmd=ReportNeighbours:ask=3b]
        Traceback (most recent call last):
          File "/snap/maas/32469/usr/lib/python3/dist-packages/twisted/internet/asyncioreactor.py", line 271, in _onTimer
            self.runUntilCurrent()
          File "/snap/maas/32469/usr/lib/python3/dist-packages/twisted/internet/base.py", line 991, in runUntilCurrent
            call.func(*call.args, **call.kw)
          File "/snap/maas/32469/usr/lib/python3/dist-packages/twisted/internet/defer.py", line 700, in errback
            self._startRunCallbacks(fail)
          File "/snap/maas/32469/usr/lib/python3/dist-packages/twisted/internet/defer.py", line 763, in _startRunCallbacks
            self._runCallbacks()
        --- <exception caught here> ---
          File "/snap/maas/32469/usr/lib/python3/dist-packages/twisted/internet/defer.py", line 857, in _runCallbacks
            current.result = callback(  # type: ignore[misc]
          File "/snap/maas/32469/usr/lib/python3/dist-packages/twisted/protocols/amp.py", line 1138, in checkKnownErrors
            key = error.trap(*command.allErrors)
          File "/snap/maas/32469/usr/lib/python3/dist-packages/twisted/python/failure.py", line 451, in trap
            self.raiseException()
          File "/snap/maas/32469/usr/lib/python3/dist-packages/twisted/python/failure.py", line 475, in raiseException
            raise self.value.with_traceback(self.tb)
          File "/snap/maas/32469/usr/lib/python3/dist-packages/twisted/python/threadpool.py", line 244, in inContext
            result = inContext.theWork()  # type: ignore[attr-defined]
          File "/snap/maas/32469/usr/lib/python3/dist-packages/twisted/python/threadpool.py", line 260, in <lambda>
            inContext.theWork = lambda: context.call(  # type: ignore[attr-defined]
          File "/snap/maas/32469/usr/lib/python3/dist-packages/twisted/python/context.py", line 117, in callWithContext
            return self.currentContext().callWithContext(ctx, func, *args, **kw)
          File "/snap/maas/32469/usr/lib/python3/dist-packages/twisted/python/context.py", line 82, in callWithContext
            return func(*args, **kw)
          File "/snap/maas/32469/lib/python3.10/site-packages/provisioningserver/utils/twisted.py", line 856, in callInContext
            return func(*args, **kwargs)
          File "/snap/maas/32469/lib/python3.10/site-packages/provisioningserver/utils/twisted.py", line 203, in wrapper
            result = func(*args, **kwargs)
          File "/snap/maas/32469/lib/python3.10/site-packages/maasserver/utils/orm.py", line 771, in call_within_transaction
            return func_outside_txn(*args, **kwargs)
          File "/snap/maas/32469/lib/python3.10/site-packages/maasserver/utils/orm.py", line 574, in retrier
            return func(*args, **kwargs)
          File "/usr/lib/python3.10/contextlib.py", line 79, in inner
            return func(*args, **kwds)
          File "/snap/maas/32469/lib/python3.10/site-packages/maasserver/rpc/rackcontrollers.py", line 276, in report_neighbours
            rack_controller.report_neighbours(neighbours)
          File "/snap/maas/32469/lib/python3.10/site-packages/maasserver/models/node.py", line 6442, in report_neighbours
            interface.update_neighbour(
          File "/snap/maas/32469/lib/python3.10/site-packages/maasserver/models/interface.py", line 1545, in update_neighbour
            neighbour, created = Neighbour.objects.get_or_create(
          File "/snap/maas/32469/usr/lib/python3/dist-packages/django/db/models/manager.py", line 85, in manager_method
            return getattr(self.get_queryset(), name)(*args, **kwargs)
          File "/snap/maas/32469/usr/lib/python3/dist-packages/django/db/models/query.py", line 581, in get_or_create
            return self.get(**kwargs), False
          File "/snap/maas/32469/usr/lib/python3/dist-packages/django/db/models/query.py", line 439, in get
            raise self.model.MultipleObjectsReturned(
        maasserver.models.neighbour.MultipleObjectsReturned: get() returned more than one Neighbour -- it returned 2!

2024-02-13 15:36:57 provisioningserver.rpc.common: [critical] Unhandled failure dispatching AMP command. This is probably a bug. Please ensure that this error is handled within application code or declared in the signature of the b'ReportNeighbours' command. [maas:pid=320095:cmd=ReportNeighbours:ask=d230]
        Traceback (most recent call last):
          File "/snap/maas/32469/usr/lib/python3/dist-packages/twisted/internet/asyncioreactor.py", line 271, in _onTimer
            self.runUntilCurrent()
          File "/snap/maas/32469/usr/lib/python3/dist-packages/twisted/internet/base.py", line 991, in runUntilCurrent
            call.func(*call.args, **call.kw)
          File "/snap/maas/32469/usr/lib/python3/dist-packages/twisted/internet/defer.py", line 700, in errback
            self._startRunCallbacks(fail)
          File "/snap/maas/32469/usr/lib/python3/dist-packages/twisted/internet/defer.py", line 763, in _startRunCallbacks
            self._runCallbacks()
        --- <exception caught here> ---
          File "/snap/maas/32469/usr/lib/python3/dist-packages/twisted/internet/defer.py", line 857, in _runCallbacks
            current.result = callback(  # type: ignore[misc]
          File "/snap/maas/32469/usr/lib/python3/dist-packages/twisted/protocols/amp.py", line 1138, in checkKnownErrors
            key = error.trap(*command.allErrors)
          File "/snap/maas/32469/usr/lib/python3/dist-packages/twisted/python/failure.py", line 451, in trap
            self.raiseException()
          File "/snap/maas/32469/usr/lib/python3/dist-packages/twisted/python/failure.py", line 475, in raiseException
            raise self.value.with_traceback(self.tb)
          File "/snap/maas/32469/usr/lib/python3/dist-packages/twisted/python/threadpool.py", line 244, in inContext
            result = inContext.theWork()  # type: ignore[attr-defined]
          File "/snap/maas/32469/usr/lib/python3/dist-packages/twisted/python/threadpool.py", line 260, in <lambda>
            inContext.theWork = lambda: context.call(  # type: ignore[attr-defined]
          File "/snap/maas/32469/usr/lib/python3/dist-packages/twisted/python/context.py", line 117, in callWithContext
            return self.currentContext().callWithContext(ctx, func, *args, **kw)
          File "/snap/maas/32469/usr/lib/python3/dist-packages/twisted/python/context.py", line 82, in callWithContext
            return func(*args, **kw)
          File "/snap/maas/32469/lib/python3.10/site-packages/provisioningserver/utils/twisted.py", line 856, in callInContext
            return func(*args, **kwargs)
          File "/snap/maas/32469/lib/python3.10/site-packages/provisioningserver/utils/twisted.py", line 203, in wrapper
            result = func(*args, **kwargs)
          File "/snap/maas/32469/lib/python3.10/site-packages/maasserver/utils/orm.py", line 771, in call_within_transaction
            return func_outside_txn(*args, **kwargs)
          File "/snap/maas/32469/lib/python3.10/site-packages/maasserver/utils/orm.py", line 574, in retrier
            return func(*args, **kwargs)
          File "/usr/lib/python3.10/contextlib.py", line 79, in inner
            return func(*args, **kwds)
          File "/snap/maas/32469/lib/python3.10/site-packages/maasserver/rpc/rackcontrollers.py", line 276, in report_neighbours
            rack_controller.report_neighbours(neighbours)
          File "/snap/maas/32469/lib/python3.10/site-packages/maasserver/models/node.py", line 6442, in report_neighbours
            interface.update_neighbour(
          File "/snap/maas/32469/lib/python3.10/site-packages/maasserver/models/interface.py", line 1545, in update_neighbour
            neighbour, created = Neighbour.objects.get_or_create(
          File "/snap/maas/32469/usr/lib/python3/dist-packages/django/db/models/manager.py", line 85, in manager_method
            return getattr(self.get_queryset(), name)(*args, **kwargs)
          File "/snap/maas/32469/usr/lib/python3/dist-packages/django/db/models/query.py", line 581, in get_or_create
            return self.get(**kwargs), False
          File "/snap/maas/32469/usr/lib/python3/dist-packages/django/db/models/query.py", line 439, in get
            raise self.model.MultipleObjectsReturned(
        maasserver.models.neighbour.MultipleObjectsReturned: get() returned more than one Neighbour -- it returned 2!

2024-02-13 15:36:57 regiond: [info] 127.0.0.1 POST /MAAS/metadata/status/4nem8e HTTP/1.1 --> 204 NO_CONTENT (referrer: -; agent: python-requests/2.22.0)
```