Mi 11 Ultra global back to global not working


Oct 25, 2021
Hey my mi 11 ultra global is on the latest stable eu right now but i need to send it to repair and would like to lock the bootloader again but i cant flash the global stock firmware. The xiaomi flasher is giving fastbooot issue and when " fixing " that it says it flashed in 0 secs but its not doing anything at all so i tried flashing directly without the flasher but it stop flashing after step 7 or so and then the phone is getting stuck in fastboot bootloop so i have to flash the eu firmware again to use the phone and i cant lock the bootloader like that.
someone knows how to lock the bootloader on mi 11 ultra?