I would suggest do a complete clean install (wiping everything but USB OTG) and making sure you got the latest TWRP from blu_spark or codeworkx. Also flash it following these instructions:
[Clean Flash] For Users with an Unlocked Bootloader and TWRP Recovery:
- Download the full ROM zip from the downloads section above
- Transfer the zip to the root of your device's internal storage
- Only needed if you are coming from Oreo or if you use an old TWRP recovery that's not the latest and Pie compatible: Remove the compatibility.zip from the downloaded full ROM zip with either MiXplorer or Total Commander (not with any other tool!) on your device itself
- Reboot to TWRP recovery (make sure you're using siankatabg's TWRP if you're on Oreo or codework's TWRP/blu_spark TWRP if you're on Pie) and take a nandroid backup of your existing ROM
- Flash Magisk Uninstaller (recommended)
- From the TWRP menu, Wipe > Advanced wipe > Select dalvik-cache, cache, system, vendor and data> Swipe to wipe
- From the TWRP menu, Install > Select full ROM zip (modified one with compatibility.zip removed, in case you're on Oreo or unmodified one, in case you're on Pie) > Swipe to flash
- Flash the latest stable Magisk in case you want to root
- From the TWRP menu, Wipe > Advanced wipe > Select dalvik-cache and cache > Swipe to wipe
- Optional: If you wish to decrypt, format data via TWRP (please note that wiping the data partition, which we did in the 5th step above, is not the same as formatting it) and after that flash Disable DM-Verity and ForceEncrypt 2.0 (OP5-5T-Treble).zip from here
- Reboot
Full instructions and downloads from ->
https://forum.xda-developers.com/oneplus-5/how-to/official-oxygenos-4-5-2-7-1-1-ota-t3627003