Speaker Not Working On Modded Gameboy Fix!

I recently modded my gameboy everything worked great. Then suddenly my speaker kept cutting in and out. When i would shake it, it would start working. when I would lay it it down it would stop working. But nothing indicated that it was the battery connectors were the problem because the gameboy started perfect everytime I had the tiniest bit of corrosion on one of the battery connectors just removed that and it started working like normal