Can't unlock Bootloader on Realme X3 SuperZoom - unable to enter fastboot mode

[michoczko]

Hello, I'd like to unlock my bootloader but I simply can't. After running a dedicated unlock "in-depth test" app, phone reboots, enters fastboot mode for a second, then reboots to system. When my phone is plugged to PC I try to type "fastboot devices" in platform tools and my phone is not visible there, however it is visible when I type "adb devices" I can not boot into fastboot mode manually either - after pressing VOL UP + POWER for a few seconds, it boots up to fastboot and then immediately restarts to system. How can I possibly unlock the bootloader?

edit: same thing happens when I try to execute "adb reboot bootloader" - boot to fastboot mode for few seconds, then restart to system immediately