Default Nexus 7 speakers flicker off when laid on back

Please help! I recently replaced LCD assembly and since then, my speakers flicker off when laid on back or when I put a case on it. So far I have I tried three sets of speakers and its the same thing everytime. Its driving me nuts and there are no threads on this issue. As far as I know, the heatsinker covers the speaker plug and it works fine except when I lay it down. What gives.

Thanks for looking.