iPhone 4 battery connection problem after screen repair

[Duders]

Hey guys first time poster here, I figured some of you might be able to help me with my problem. After repairing the screen the phone sometimes won't power on or will randomly reboot. I figured out that if I shake it it sometimes does this. After figuring this out I took the phone apart. If i press on a specific part on the battery connector cable, the piece that connects to the mainboard, the phone will shutdown. Are any of you familiar with this problem and do you think that the problem could be solved just by ordering a new battery for the phone or did I maybe ground out something somewhere?