Maybe your gapps are causing some problems. I dont use gapps and dont have problems updating.
Have you removed pin/password/fingerprint/face data and flashed latest firmware? That also causes problems while updating.
Make sure u flash dm variety zipIssue 1:
Your latest rom from 06/12 cannot be flashed, it says invalid zip file format.
If I tried the second latest, 27/11, I can flash it, but one I reboot, I see Powered by Android and then the phone reboots back to twrp mode.
It won't boot on this rom.
I wiped cache, dalvik, data and followed your instructions, with the firmware you mentioned.
Any advice how to get it working on Oneplus 5?
Arrow works better, I don't understand why to produce identical firmware without adding new features.