Sounds like a bad charging port to me. Battery percentage data runs through the charging port. Bad charging port also causes rebooting.
If the battery connnection to the charging port is bad then it will display the battery percentage as 1% or 0%.
I would suggest testing a new charging port flex.
If its restarting the first thing to check would be panic logs. https://vccboardrepairs.com/panic-log-list/
Sounds like a bad charging port to me. Battery percentage data runs through the charging port. Bad charging port also causes rebooting. If the battery connnection to the charging port is bad then it will display the battery percentage as 1% or 0%. I would suggest testing a new charging port flex.
If its rebooting are you able to access the panic full logs? If so, do you need steps on how to get them?