@minhnewpro please reupload the files in "System Dump 2.19.400.1 Oreo U Ultra Dual SIM". I tried to relock bootloader in order to downgrade to nougat after flashing the rooted oreo from #1 but I got stuck in download mode, I tried to flash hboot from the tut at https://vnrom.net/2018/03/rom-stock-ruu-zip-cho-htc-u-ultra-ocean-note/ but fail all the time