When the CPU crashes and the blanking fails to kick properly the lamp columns may lock on and overheat the base limit resistors to the point they burn. Probably why you will see the area around the lamp column resistors often burned up.

Pretty sure the burn smell was just the lamp columns resistors heating when locked on during the time time the CPU crashed and the blanking stayed high. If the CPU crashes and the blanking stays high is also a reason the solenoid fuse will blow. Both the solenoid fuse popping and lamp column resistors heating up are often a symptom of the CPU that jumped out of a program but there was still enough activity at the display PIA to keep the blanking stimulated and high.

Did you check if the +5v is stable and good? If the 5v is good when he game powers OK gently flex on the pcb near the U25 chip to see if that makes it crash (IC socket problem).

Someone has replaced U25 in the past as its in a chip socket. That gives you a good excuse to get NVRAM since a socket is already fitted. If the U25 error message is not consistent and it sometimes boots the chip is probably not defective but something else is going on making the CPU not be able to access it and make the CPU crash. Low 5v is a good first step. Previous rework being suspect would be my #2 .