The ROM corruption you had was a known software issue that was fixed in later ROMs. It was possible for the ROM to become corrupted during a power cycle.

The reset problem is an issue with the 5V power supply and is unrelated to the ColorDMD. The ColorDMD draws almost all of it's power off 12V. 5V is used only for USB and as an enable signal to turn on the board's 1.2V regulator.

To confirm, you can unplug the ColorDMD, hit both flippers at the same time and still see resets. This is a common issue that is usually related to a failing bridge rectifier or capacitor on the 5V supply. The 5V signal fluctuates and falls below a watchdog, triggering the reset.

A problem on the unregulated 12V supply can produce weak flippers but not game resets. Usually due to the same cause, though, a failing bridge or cap.

Resets are caused by a drop in 5V.

If your 12V supply is low you may have another problem but it is extremely unlikely that activity on the 12V supply is causing the reset. 12V and 5V come from different transformer windings and do not normally affect one another. (The exception would be if you have an aftermarket Kahr board installed which generates a dedicated 5V for the CPU from the 12V supply. In this case a sudden drop in 12V could affect the CPU.)

Resets are often related to voltage fluctuations on the 5V supply that are caused by coupling of high-speed switching/firing of the high voltage solenoids, and a failing bridge/cap or resistive connection in the 5V supply.

If your 5V output is already low, resets are more likely to occur because it takes a smaller dip to trigger the watchdog reset logic.

Voltage fluctuations can often be detected using a DMM to monitor the 5V test point, and flipping both flippers at the same time.