Was trying to print the x-motor-bracket in ABS but had a hard time preventing it from lifting the corners, so re-designed it for easier printing (cutting the corners) and while I was at it, opened the belt tunnels a bit as the belt was dragging
also made a stronger z-bearing-clamp with four screw holes, to use these you will have to drill four extra holes in the x-arm, just print the z-motor-bracket first and use is as drilling template
..and cut the corners of Bobtidey's z-nut mod to make it fit in nicely with the x-motor-bracket mod
Please note that I cut of the arm for the sensor, so you will have to glue one on, or as I did, mount one using the micro switch screw holes
I had the same issue when I printed the original X motor bracket.
Cutting the corners seems to do the trick, also raising the bed temperature from 110 to 120C might have helped - forgot to note the print was on Kapton tape sanded with P400
..and remember to scale up a bit if ABS, 0.6% for the filament I use at the moment