iPhone 7 freezing since screen replacement

Hi Guys,

Wonder if anyone can shed some light on this.

Replaced an iPhone 7 screen the other day. When i changed the screen and powered it on the first time, the screen was unresponsive, so i had to lock it and then the screen came back to life and it worked fine when i tested it. However the customer left it for a couple of days and advised me that it kept freezing. So i went back to change it for another screen but the same thing is happening.

I will note that the first screen i used was a copy, but the second screen was OEM.

Thanks in advance.