Midway started using these brown Palmer IC sockets around that time that proved to be unreliable resulting in frequent MPU crashes. There is also the issue of past battery damage that could cause similar issues.
Can you post a picture of the MPU and a closeup of the battery area? That would help in the diagnosis.

Remove the battery pack and get an NVRAM. Weebly is out but you can still find them on eBay.
If you are using non rechargeable batteries and do not have a blocking diode installed the batteries will be damaged and will damage the board.