Actually TWRP itself sometimes doesn't restore partation correctly so finest way is to restore import partation like system, Efs, persist, data using fastboot commnads.I've tried a few times now with Denizz TWRP and when taking NANDroid I get no errors. When flashing back NANDroid I get no errors (reported) in TWRP. But after a reboot to system I get a bootloop.
The bad thing... for some reason that bootloop NEEDS a full system recovery and it means I need to drive to an OnePlus servicecenter (or send it in) to have my whole system recovered. Good thing is that this service is free of charge (warrantee) but it takes me 1 hour 45 minutes to drive there, and another 1 hour 45 minutes to drive back home.
I don't trust to take NANDroids anymore, and that sucks, because in the end it is meant to be a security copy when I make stupid mistakes (which I will).
But for me TWRP show only data partition restoration error so I untiked that and it worked