iPhone dead after screen replacement

Hi guys, I'm after some advice on my phone, I smashed the original screen on the phone so I had an aftermarket replacement fitted, I had a guy come out to my house and do it for me it took him about 20 mins everything was working fine (apart from a little crackle in the ear peice) until about 2 weeks ago ( it lasted about 3 weeks) I put it on charge one night and in the morning it was totally dead so I had the guy out again who replaced the screen and everything worked fine again until I plugged it in again last night and woke up to another dead phone so I've rang the company today and they will try and get to me tomorrow. So basically I am just looking for some advice before he comes, do you think this could be long screw damage? Would a long screw fault be faulty from the start rather than week(s) down the line? Are there any fuses in iPhones? With the crackling of the speaker, perhaps the plug is not pushed into the motherboard properly, do you think this could cause a short? I obviously don't know anything about phones and I'm just trying to think what it could possibly be, I don't want him coming tomorrow and fitt another new screen and then it goes again because not having a phone is a right ball ache lol

Or do you think I could of just got 2 $@$* screens?

Thanks in advance all