I tried reproducing this on the tip of unmaintained/zed (c32eb5669a) and on current master, but I could not.

Is this always happening for you? If not, how frequent is it? Do you see any factors influencing its frequency? Do you have steps to reproduce it?

On a system where the trunk ends up working properly I get the same logs as you:

rubasov@devstack1:/opt/stack/neutron$ sudo journalctl -o short-iso-precise -u devstack@q-agt -S -1h | egrep tap3bb2174c-e9 | head -10
2024-06-20T08:14:50.593451+0000 devstack1 neutron-openvswitch-agent[1018]: DEBUG neutron.agent.common.async_process [-] Output received from [ovsdb-client monitor tcp:127.0.0.1:6640 Interface name,ofport,external_ids --format=json]: {"data":[["4834efe7-27fc-4f8a-8217-8b925414dc5a","insert","tap3bb2174c-e9",["set",[]],["map",[["attached-mac","fa:16:3e:6f:92:ef"],["iface-id","3bb2174c-e959-4f29-a165-6a69ea731da7"],["iface-status","active"],["vm-uuid","c2584e6e-f6e7-4e18-b106-39f7c2533e30"]]]]],"headings":["row","action","name","ofport","external_ids"]} {{(pid=1018) _read_stdout /opt/stack/neutron/neutron/agent/common/async_process.py:268}}
2024-06-20T08:14:50.596984+0000 devstack1 neutron-openvswitch-agent[1018]: DEBUG neutron.agent.common.async_process [-] Output received from [ovsdb-client monitor tcp:127.0.0.1:6640 Interface name,ofport,external_ids --format=json]: {"data":[["4834efe7-27fc-4f8a-8217-8b925414dc5a","old",null,["set",[]],null],["","new","tap3bb2174c-e9",-1,["map",[["attached-mac","fa:16:3e:6f:92:ef"],["iface-id","3bb2174c-e959-4f29-a165-6a69ea731da7"],["iface-status","active"],["vm-uuid","c2584e6e-f6e7-4e18-b106-39f7c2533e30"]]]]],"headings":["row","action","name","ofport","external_ids"]} {{(pid=1018) _read_stdout /opt/stack/neutron/neutron/agent/common/async_process.py:268}}
2024-06-20T08:14:50.941812+0000 devstack1 neutron-openvswitch-agent[1018]: DEBUG neutron.agent.common.async_process [-] Output received from [ovsdb-client monitor tcp:127.0.0.1:6640 Interface name,ofport,external_ids --format=json]: {"data":[["4834efe7-27fc-4f8a-8217-8b925414dc5a","old",null,-1,null],["","new","tap3bb2174c-e9",1,["map",[["attached-mac","fa:16:3e:6f:92:ef"],["iface-id","3bb2174c-e959-4f29-a165-6a69ea731da7"],["iface-status","active"],["vm-uuid","c2584e6e-f6e7-4e18-b106-39f7c2533e30"]]]]],"headings":["row","action","name","ofport","external_ids"]} {{(pid=1018) _read_stdout /opt/stack/neutron/neutron/agent/common/async_process.py:268}}
2024-06-20T08:14:51.112215+0000 devstack1 neutron-openvswitch-agent[1018]: DEBUG ovsdbapp.backend.ovs_idl.transaction [-] Running txn n=1 command(idx=0): DbSetCommand(table=Interface, record=tap3bb2174c-e9, col_values=(('external_ids', {'attached-mac': 'fa:16:3e:6f:92:ef', 'iface-id': '3bb2174c-e959-4f29-a165-6a69ea731da7', 'iface-status': 'active', 'vm-uuid': 'c2584e6e-f6e7-4e18-b106-39f7c2533e30', 'bridge_name': 'tbr-141d065f-0', 'trunk_id': '141d065f-0e7c-4ad1-86c0-47c6a0329298', 'subport_ids': '[]'}),)) {{(pid=1018) do_commit /usr/local/lib/python3.8/dist-packages/ovsdbapp/backend/ovs_idl/transaction.py:89}}
2024-06-20T08:14:51.121507+0000 devstack1 neutron-openvswitch-agent[1018]: DEBUG neutron.agent.common.async_process [-] Output received from [ovsdb-client monitor tcp:127.0.0.1:6640 Interface name,ofport,external_ids --format=json]: {"data":[["4834efe7-27fc-4f8a-8217-8b925414dc5a","old",null,null,["map",[["attached-mac","fa:16:3e:6f:92:ef"],["iface-id","3bb2174c-e959-4f29-a165-6a69ea731da7"],["iface-status","active"],["vm-uuid","c2584e6e-f6e7-4e18-b106-39f7c2533e30"]]]],["","new","tap3bb2174c-e9",1,["map",[["attached-mac","fa:16:3e:6f:92:ef"],["bridge_name","tbr-141d065f-0"],["iface-id","3bb2174c-e959-4f29-a165-6a69ea731da7"],["iface-status","active"],["subport_ids","[]"],["trunk_id","141d065f-0e7c-4ad1-86c0-47c6a0329298"],["vm-uuid","c2584e6e-f6e7-4e18-b106-39f7c2533e30"]]]]],"headings":["row","action","name","ofport","external_ids"]} {{(pid=1018) _read_stdout /opt/stack/neutron/neutron/agent/common/async_process.py:268}}

One random idea: Could this affect you maybe?
https://bugs.launchpad.net/neutron/+bug/1930414/comments/42 and comment#43