Problem is I think he has the old TWRP by Mr.Raines/Mr Tomatico, it would not let me flash another TWRP as an image when I had tried it and wanted to change back. I had to fastboot flash the other TWRP.
TWRP recovery 3.2.1-0 for weekly ROM 7.12.21_v9 - Android 7.0
I flashed official global ROM 8.7.12 for no reason (fingers were itchy), ended up it asking me to decrypt my data partition on TWRP.
Just press cancel and format the data first, then wipe everything else.
Flashed back xiaomi.eu ROM 8.7.12 without any issues.