yeah, it's also a requirement to have a bootloader from .236 fw.I'm fairly certain it's c6903. I just checked it with Sony's flashtool (Emma) and apparently I never had the newest version on it. I flashed it and flashed Nougat again. Now it works... When the heck did they bring out that version? And sorry for the trouble.
Now if you flash recovery via fastboot, you can boot there from powered off state with power-down button and vol down