Failed digitizer repair, diagnostic please!

OK major screw up... So I'm used to repairing phones and I've taken on this iPhone 6s which had a smashed screen, I thought no issue. During disassembly I stupidly slipped and put a hole into the battery fml. I replaced it hoping nothing is messed up but the device was of with no battery acid leaking, just the smell and battery heat. I replaced the digitizer and powered on, the screen doesn't display the apple logo but goes to home screen, works until touchscreen is used and then goes black, still on and all buttons work etc, I hope dodgy digitizer so I replace it, same issue. Then I notice I might have misplaced a few screws in the wrong holes, yeah not my day. Every once in a while the phone will fully operate for 1 min or so then randomly go black, sometimes when pressure is applied but it's not regular. What might be the issue and fix or is it just beyond repair? Thank you