These are 99% errors coming from the MQTT plugin for Octoprint. The HA forum post says that since I am not some MQTT guru I need to contact the provider of the messages.
SO. If you are reading this, and you are one of the developers/ maintainers of this project:
Are you aware that this is happening???
Sorry if I seem ters. I'm just tired of people changing shit every time I got it all working properly...
As mentioned in the issue you posted, I think this is coming from the Home Assistant plugin. From what I can tell it seems that this was addressed in the latest version.
I'm a little confused now. These looked like two separate plugins, but I guess both are needed for MQTT --> HA. And, I could have sworn I just recently updated both OctoPi setups. I will update again, and possibly have to purge the MQTT entity cache.