No, i did not perform any additional steps, apart from downloading and running the .bat. First through Powershell, then by just right clicking it and running it as administrator (disadvantage of that is that it closes when it is finished, and you cannot see what went well and what failed if...
Ok guys, good news. I just kept on trying and the 5th attempt made it. In the end, used CMD, but I don't think it really makes a difference.
I had the idea that keeping the mouse moving during the process helped. But that could also just be superstition.
Bottom line; don't panic if it fails...
Also stuck in fastboot unfortunately. Mi 11 Pro with 12.5 Stable via Administrator Powershell with extracted ZIP on desktop in 'Xiaomi' folder.
File: xiaomi.eu_multi_MI11Pro_MI11Ultra_V12.5.2.0.RKACNXM_v12-11-fastboot
MD5: 18E56D60DEF6BC08FD57C8BBE7730092
First attempt:
Writing 'qupfw_ab'...