Tap To Wake not working when phone is on the table

Hello everyone,

I have faced a pretty weird issue on an iPhone 11 I recently repaired. The back housing and the screen were completely shattered, but fortunately i had a new housing pulled from a working phone.

I swapped the logicboard and all relevant components e.g. cameras, antennas etc. into the new housing, installed a refurbished OEM screen and transferred screen data onto the new one.

The phone works completely fine, Face ID is working, TrueTone is restored, BUT:

Tap to Wake does not work if the phone is placed on a flat surface, e.g. my desk.

The ridiculous part? The feature does work fine if I have the phone in my hands or a Lightning cable is plugged into the port (no need to even connect it to power!)

Tried another replacement screen —> problem persists.

Updated the phone from iOS 14.7.1 to iOS 15 Developer Beta 4 —> problem persists.

I assume a grounding issue inside the charging flex, so my next step would be to replace it with another OEM part. If this doesn’t resolve the issue, I’m pretty much at a loss.

Has anyone else faced this issue?

Thanks and greets from Germany!