One problem as I see it is that Tevo has chosen to hang the z-screw in the flexible coupler, in addition the engine bracket is quite neat which together gives you a fairly unsteady linear unit to the x-axis, but it is quite easily fixed with a extra support

Instead of a locking ring resting on the ball bearing, I just put a small distance ring between the motor clutch and the bearing.

To further increase precision, I am currently working on an upgrade to two z-screws, more info will come when I finish.

Manufactured / printed parts:

• https://www.thingiverse.com/thing:2251730

Parts to buy:

• Ballbearing 608: https://amzn.to/3mqKoV2
• 2x M4 T-nut: https://amzn.to/36IrNyQ