No answers?!
Anyway, it seems that some X3000 (like mine) is flashed with non-functional Uboot! When I try to flash a firmware using the Uboot debrick method, the modem reboots without any changes - all my firmware’s settings are still unchanged!
Can someone test this Uboot on his X3000? And btw, that’s why I have asked for latest Uboot, although I suspect that X3000 modems are flashed during factory with a corrupt Uboot.