This is the error by the way:

http://paste.openstack.org/show/752159/

2019-05-28 13:40:16.610 159865 ERROR nova.api.openstack.wsgi [req-1ca4c1d0-9f6f-4a04-860d-1d3d03a0d063 9fb4630d74ad49e8ac9f4e8a72b8cafb 504ea0a356ca4066aaa617daff869463 - default default] Unexpected exception in API method: nova.exception.ObjectActionError: Object action obj_load_attr failed because: unable to load uuid
2019-05-28 13:40:16.610 159865 ERROR nova.api.openstack.wsgi Traceback (most recent call last):
2019-05-28 13:40:16.610 159865 ERROR nova.api.openstack.wsgi   File "/usr/lib/python3/dist-packages/nova/api/openstack/wsgi.py", line 801, in wrapped
2019-05-28 13:40:16.610 159865 ERROR nova.api.openstack.wsgi     return f(*args, **kwargs)
2019-05-28 13:40:16.610 159865 ERROR nova.api.openstack.wsgi   File "/usr/lib/python3/dist-packages/nova/api/validation/__init__.py", line 110, in wrapper
2019-05-28 13:40:16.610 159865 ERROR nova.api.openstack.wsgi     return func(*args, **kwargs)
2019-05-28 13:40:16.610 159865 ERROR nova.api.openstack.wsgi   File "/usr/lib/python3/dist-packages/nova/api/openstack/compute/migrate_server.py", line 56, in _migrate
2019-05-28 13:40:16.610 159865 ERROR nova.api.openstack.wsgi     host_name=host_name)
2019-05-28 13:40:16.610 159865 ERROR nova.api.openstack.wsgi   File "/usr/lib/python3/dist-packages/nova/compute/api.py", line 205, in inner
2019-05-28 13:40:16.610 159865 ERROR nova.api.openstack.wsgi     return function(self, context, instance, *args, **kwargs)
2019-05-28 13:40:16.610 159865 ERROR nova.api.openstack.wsgi   File "/usr/lib/python3/dist-packages/nova/compute/api.py", line 213, in _wrapped
2019-05-28 13:40:16.610 159865 ERROR nova.api.openstack.wsgi     return fn(self, context, instance, *args, **kwargs)
2019-05-28 13:40:16.610 159865 ERROR nova.api.openstack.wsgi   File "/usr/lib/python3/dist-packages/nova/compute/api.py", line 153, in inner
2019-05-28 13:40:16.610 159865 ERROR nova.api.openstack.wsgi     return f(self, context, instance, *args, **kw)
2019-05-28 13:40:16.610 159865 ERROR nova.api.openstack.wsgi   File "/usr/lib/python3/dist-packages/nova/compute/api.py", line 3516, in resize
2019-05-28 13:40:16.610 159865 ERROR nova.api.openstack.wsgi     context, instance.uuid)
2019-05-28 13:40:16.610 159865 ERROR nova.api.openstack.wsgi   File "/usr/lib/python3/dist-packages/oslo_versionedobjects/base.py", line 184, in wrapper
2019-05-28 13:40:16.610 159865 ERROR nova.api.openstack.wsgi     result = fn(cls, context, *args, **kwargs)
2019-05-28 13:40:16.610 159865 ERROR nova.api.openstack.wsgi   File "/usr/lib/python3/dist-packages/nova/objects/request_spec.py", line 531, in get_by_instance_uuid
2019-05-28 13:40:16.610 159865 ERROR nova.api.openstack.wsgi     return cls._from_db_object(context, cls(), db_spec)
2019-05-28 13:40:16.610 159865 ERROR nova.api.openstack.wsgi   File "/usr/lib/python3/dist-packages/nova/objects/request_spec.py", line 510, in _from_db_object
2019-05-28 13:40:16.610 159865 ERROR nova.api.openstack.wsgi     context, spec.instance_group.uuid)
2019-05-28 13:40:16.610 159865 ERROR nova.api.openstack.wsgi   File "/usr/lib/python3/dist-packages/oslo_versionedobjects/base.py", line 67, in getter
2019-05-28 13:40:16.610 159865 ERROR nova.api.openstack.wsgi     self.obj_load_attr(name)
2019-05-28 13:40:16.610 159865 ERROR nova.api.openstack.wsgi   File "/usr/lib/python3/dist-packages/nova/objects/instance_group.py", line 355, in obj_load_attr
2019-05-28 13:40:16.610 159865 ERROR nova.api.openstack.wsgi     action='obj_load_attr', reason='unable to load %s' % attrname)
2019-05-28 13:40:16.610 159865 ERROR nova.api.openstack.wsgi nova.exception.ObjectActionError: Object action obj_load_attr failed because: unable to load uuid

This is on a Rocky deployment.