D-Pad Down actives Start Button (Sometimes)

After a short time in game the down button acts as the start button and then as the down button again. This is also the case for Select/UP, Left/B and Right/A.

I've done some work on the Gameboy and haven't found any shorts.

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crwdns2889612:0crwdne2889612:0 0
crwdns2934285:0crwdne2934285:0