Phone works perfectly for 2 mins then Blue screen and restarts?

So after an issue with the phone not charging, I replaced the charging port (oem apple iPhone 5s from donor phone) , and the battery as the battery had decreased its ability to hold a charge.

Rebooted phone and it is working, however after a couple of minutes of use it crashes with a blue screen for a second before restarting.

I have researched this and the BSOD appears to be a different fault caused by the overtightening of screws damaging the 7 bus lines on the PCB. I am sure this is not my fault.

So I have tried different batteries, checked and double checked the repairs I have done (charging port).

I have done the basics of restore and reset with no change in prognosis.

I am sure its something simple any ideas?

The only thing I haven't done is changed the screen, there is as always a possibility that a cable has been damaged here during works, but for now its working as normal??

Please Help.