Correct me if I am wrong.
Is your device bootloader unlocked, TWRP and rooted on Android Build 9.0 (Pie).
At this moment I suggest you remain on Build 9.0.x.x and not bother updating to Build 9.1.x.x.
Unless you have some urgent need to update to Build 9.1. ?
And if you update to Build 9.1...