Let me give report on sdcard issue. If needed, I'll give more details.
N910F on incremental upgrades, currentyl ripee v 20190322, addonsu, no magisk, no gapps. 64g sdcard as external vfat applied, twrp-3.3.0-0-trlte
If sdcard receives a huge (?) load, reboot happens, after the reboot LOs fails...