Phone screen stops working after replacing it more then once

So I cracked my s21 phone screen so I decied to fix it after I fix it it worked fine for like 30mins after I was done and the screen just went black so I thought it was just that screeb so I decidedto put into the old screen so I can use my phone till the new screen comes in buy after I was done putting everything back in the old screen it work for like 3 hours till I plugged it in and just died again. The phone still makes noise and vibrants what could be the issue