https://www.tunabellysoftware.com/balance_lock/
Of course it's kind of messed up that this is necessary, but there it is.
I don't care about the why this happens. I don't care that the DAC I use is really old. This is just a thing that shouldn't be happening on a modern operating system that has such an apparently old pedigree in high quality audio.
(Context: I’ve only had this happen when I connect my Caldigit thunderbolt dock. This dock has always caused the audio to change balance to ~90% left since I unboxed it, so I suspect it has something to do with how the audio interface presents itself to the system, but I don’t know for sure.)
It is absolutely wild this bug exists.