Sockets and chips.
Chip legs are (typically unless gold plated) tin plated.
If you are in a humid environment, tin corrodes resistive. It doesn't make much to muddle the 0's and 1's.
Start by disconnecting the power.
Then remove each ROM chip carefully using the correct tool, clean the legs using a fiberglass scratch pen (Amazon) and treat with DeOxit. Carefully reinstall the chips getting the orientation correct. Power it back up and see what you get.