An eBay purchase that has some issues, but came with the original instructions. Follows a similar game design to “Simon”
So with battery I would get intermittent power, and sad beeps.
To dismantle, there are no screws it a set of clips along the edges. The keypad is held in place by plastic rivets and you have to break or melt those to separate the keypad front from the backing plate.
So the first issue was this was not it’s first rodeo. It had water damage and also the 9 metal pins that hold the keypad had broken off at the solder level.
The easiest repair was just to replace the old metal pins with 22 gauge wire.