Unable to flash any non-stock ROM on 910F

Hello everybody,

I run into a strange problem with my 910F (never had this problem before with other smartphones).
Any non-stock thing I try to flash (custom recovery, ROMs like Evolution, Ketan, CM, BattleHero, SimpleROM, etc.) lead to a boot-loop.
It simply refuses to boot.
The only way to recover it is to flash from Odin N910FXXU1BOC5_N910FPHE1BOD1_N910FXXU1BOC4_HOME.tar .md5 ROM.
Then it boots, upgrades to Marshmallow, but it's a pure Samsung ROM with lots of bloatware and no root.
Attempt to flash root (like UPDATE-SuperSU-v2.40.zip) from recovery mode also fails.

Any idea what could be?

Thanks!