I know on the sitdowns they go through a lot of abuse from people getting in and out of them, the boards are mounted in a cage underneath the seat.
could be that, or it could just be the nature of the beast, but they seem to get chip creep a lot. the game boards are a series of interlocked ones, so if you have any problems at all I'd yank em out and give them a cleaning and a reseating.
gobbles voltage too, since it's so many parts. I forget the exact number I had at the power supply, but you have to dial it up a bit from the PSU going to a little power filter board, and then going to the PCB cage (which is another filter board)
if you get to a point where you need to replace a PSU on these, make note of the wire colors, cause Sega uses their own color scheme. like I wanna say white was ground, brown's 3.3V, yellow is +5V, etc. (DON'T QUOTE ME HERE, just follow how they're going to the existing ones lol)
uprights should go through way less wear and tear than the twins I got though. I saw your thread about linking them, Sega just does stuff weird. you might luck out and have the comm boards in yours.