A complete system backup without root with TWRP Custom Recovery including EFS / IMEI on external microSD card can protect against nasty surprises. Select the entries Boot, System, Data and EFS.
Note: The EFS (Encrypting File System) file system contains all “important” data about device code (IMEI), security zone, product code, serial number and MAC addresses for Bluetooth and WLAN. All hash values of the system files are also stored there.
If necessary, the system backup can be restored via TWRP RESTORE.