server won't stop, seems to loop endlessly on an "aborted connection" error

Hello - I have encountered a server instance that seems to no longer be able to shutdown normally. It looks to be trying to endlessly kill an aborted connection, with messages that repeat like these:

2021-04-13 10:19:17 0 [Warning] Aborted connection 5 to db: 'unconnected' user: 'unauthenticated' host: '' (KILLED)
2021-04-13 10:19:19 0 [Warning] Aborted connection 5 to db: 'unconnected' user: 'unauthenticated' host: '' (KILLED)
2021-04-13 10:19:21 0 [Warning] Aborted connection 5 to db: 'unconnected' user: 'unauthenticated' host: '' (KILLED)
2021-04-13 10:19:23 0 [Warning] Aborted connection 5 to db: 'unconnected' user: 'unauthenticated' host: '' (KILLED)

There is nothing connected to the instance when this happens, and there are no aborted connections reported in the "Aborted_connects" value from "show status", it is set to 0.

This has persisted across restarts and a reboot of the server itself.

The server process keeps running, but it is no longer reachable on port 3306 when it gets in to that loop. It will stay that way endlessly, it needs to be sent a "kill -9" to end the process.