Mystery solved. Ditto for the issues with SD card reads.
The board previously had a short some few months ago because the aux pad made contact with the aluminum hilt. We re-wired it to another aux pad 2, which seemed to solve the issue. However, shortly after doing this the issues with SD card reading as well, the random power ons, and the other plethora of issues I detailed in the other thread, started to appear.
The installer working on this repair was able to replicate the issues I was experiencing and checked over continuity between pads as well as the casing on the hilt - no failures.
A new board was wired in and all the issues mentioned were irreproducible afterwards.