As @Mike_O_Neill mentioned, there’s little mention of this problem on the forum at the moment, so the issue is most likely related to the configuration of your problematic core - something about that device, or the way in which it connects to your “unchanged network” is triggering an edge case bug. If I were you, and I’ve mentioned this before, I would edit your original post to include as much info as possible regarding the devices in question, your network, connected audio devices and so on.
When you initially raised this problem in 2020 you were advised to try connecting your core to your primary router rather than going through a bunch of wifi extenders. Did you try that?