Changing /system/build.prop issues on fully rooted and DM-verity removed device SO, I have an MT6739 dveice with Android 8.1, it's not A/B seamless, and it is not TREBLE. 

I have used a tried and tested method to remove DM-Verity. On this device it was in the DTB, in the boot and also in the vendor partitions. I use Magisk to get me root and I have removed and installed lots of /system/apps, changed the audio, bootanimations etc on the device. I even changed the backgrounds and tweaked the Launcher.

However whenever I come to change anything in /system/build.prop the device bootloops!

I have tried this with Magisk DM-verity ON/OFF with no effect. I also copied back a build.prop from my PC and it worked fine again. So, something must be looking up the build.prop and checking for changes.

All I have done is change the ro.product.model property to be super sure nothing in the build.prop is incorrect. I have tried with setting permissions (644, for some reason they are 600 (RW - - ) on the device so tried that too).

There is a build.prop in the /vendor partition. i have heard of this checking the fingerprint of the system/build.prop, but they are different anyway on the stock ROM.

I also tried just copying the build.prop from /system into here so they were identical.

Fresh out of ideas!!

Does anyone know what is going on here. I can literally change anything I want on the device as normal/pre-verity days except for the build.prop settings.
See when you did the DM Verity patch, have you patched the boot.img to support Android 8.1? if working on Win can use ClassyKitchen. If working on Linux, AIK Linux is the way to go. i'd suggest using classykitchen and patch for DM verity and enable 8.1 support. worked for me. running 8.0 Oreo. ;)