It is known that TWRP does not back up
/data/media as you can read
here and on other posts on this site
How can one bypass this?
Android Enthusiasts Stack Exchange is a question and answer site for enthusiasts and power users of the Android operating system. It only takes a minute to sign up.Sign up to join this community
There's an app that's just been released (tested on Moto X Play) that bridges the gap between Nandroid and full backup and backs up photos, videos, game data etc, which wasn't possible earlier
Tipatch patches TWRP to backup contents of internal storage (emulated SD card) as part of Data, thus preventing data loss. Internal storage typically includes items such as photos, videos, downloads, game data, and other assorted files.
A side effect is that wiping "Data" will also wipe internal storage. This cannot be fixed.
Programs (instead of using app) for all OS's available on Github
I am not affiliated in any way with the app or developer and wanted to share a tip-off from a friend
Edit: Also now available in Izzy's F-droid repo