iPad 7 Rapid Battery Drain

Hello

I repaired a clients iPad 7 and it came back back with in 2 days with "rapid battery drain"

Pre and post repair I checked that the battery charged at least 5%.

I did confirm that after getting the iPad back that it will loose 100% charge over night in stand by.

I checked the battery on 3u tools and it said 87% capacity / life.

I replaced the battery any ways as 3u isn't always correct and the "new" battery (taken from a donor iPad) was 95%

Same issue

I tested with an original screen (one i removed with out breaking) with the same issue.

Home button flex is all original

The full restore and update was done with the same issue

Any idea's?

Note - I can't prove / disprove the iPad wasn't doing this before I received it for repair as I only ever make sure it charges at least 5% as prev mentioned

Thanks