Im having the same issue youre describing. I can root but then there is no data or wifi. Its strange. OP, you have any insight?5.1.11 Boot + magisk 16.6 or 16.7, I tried both today the result is the Phone boots, but there after I have no root (magisk Manager keeps crashing) and no Wifi either.
Need to restore back to 5.1.6 which is that last boot image I've had success with and magisk 16.3 compiled for treble.
However I've a hell of a time doing so, flashing 5.1.6 boot. thenhung at "ANDRIOD" on me. So I tried a TWRP restore (everything except for EFS), Which is why I have a TWRP backup in the first place however that returns a black screen so worse than useless.
So how to recover from this situation where boot is bad. I went all the way back to 5.1.7 then upgraded online to 5.1.9 and then offline to 5.1.11
1. Backup TWRP backup off the phone.
2. Re-flash stock, then upgrade (may as well to latest), 5.1.11 as of now.
This clears Data and storage!
3. This gives you a clean slate of boot, system and vendor
4. Copy TWRP back top the phone
5. Flash the same system as previously used.
6. Boot into TWRP and restore only DATA
7. reboot your phone should be the same as previously
8. Optional reboot and flash Root if desired, You could do this as part of 7, but to be safe I waited till after the first boot.