Hi,
Drahti is right.
As I've already written, once it's flashing, a lot of things are working (in particular the microprocessor, partial access to the roms and rams needed to make these I/Os, the flashing diodes and part of the LCD).
One (if more than one, there's little chance of the program working and continuing) bad contact with a ROM pin can generate errors when checking the hardware when the device is powered up (checking the pieces on the chessboard, for example).
The RAMS are soldered, so only the ROMs need to be removed and replaced in their socket.
With a medium-sized flathead screwdriver inserted between the IC and its socket, rotate the screwdriver through 15-30°, then to the opposite side, and repeat until it is completely extracted. The aim is to avoid bending the pins. Of course, pay attention to the direction of the circuit when reinserting it.
In any case, this type of 8-bit hardware is repairable (no comparison with the GALs on my Risc 2500).

Cordially.

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