I don't want to speak too soon but it looks like recapping the LV supply did the trick. Ripple on all of LV rails is much lower. I've been cold starting the scope for the past few days and letting it run for hours at time and it seems stable so far. I replaced the battery and lubricated the fan while I was in there as well.
In the end, it looks like ripple on 5V supply was tripping the "Power-On Reset" circuit on the A16 processor PCB causing the microprocessors to halt.
Appreciate the encouragement and advice from the group to get this solved.
