Battery connector crackling, apple logo flashes and dissapears

Hello,

As stated in the title, I've opened my Ipad because screen went black but still made sound when charger was plugged, I shined some light with flashlight but there was still no screen, opened it without a problem, detached and reattached the connector on the back of the screen and now apple logo appears for 0.7-0.8s and then screen goes black and battery connector makes crackling noise, i removed the motherboard, inspected the battery connector and it's all good. Does anybody know what's going on? How can i troubleshoot or isolate the problem?