Invalid Xiaomi 14 Pro Shennong EU rom storage stays full even after factory reset

[novicebgr]

Hi everyone. I've unlocked bootloader and flashed EU rom in March 2024. It worked fine until now. No matter that I've deleted everything from the storage and
done factory reset, the phone storage still stays full as if no reset has been done, as on the attached screenshot.
Any solutions or suggestions how to recover the phone back to normal?
Is this the same issue as "find device storage corruptted" error where the persist.img needs to be reflashed via TWRP or is it something else? Hardware bug?
Thanks in advance!

Actually the phone is not mine, belongs to a girl. So after she did factory reset approx. 16GB storage space were cleaned, but still somehow more than 203GB stay still busy:

Any ideas how is this possible?

 

[gogocar62]

How was the factory reset performed?
If you perform a "factory reset" in TWRP, the data from the storage will not be erased.
You need to do a "Format Data" in TWRP.

 

[novicebgr]

A Wipe through TWRP recovery did the job, thank you very much! The first time she did the reset through the Android settings option.
So is this bug common? Shall she expect this may happen again? She said she is working with big video files.