Model originally uploaded to Thingiverse at https://www.thingiverse.com/thing:2941767.
Z Axis Anti-Rotation Packer\Wedge for the Zonestar P802QR2
Wow, that's a mouthful. Basically due to the design of the stepper motor mounting tab when tension is applied to the X axis drive belt the Z axis stepper motor rotates off the perpendicular ( well spotted " Mr John").This is a bracket\packer when inserted between the Z axis stepper motor and the heat bed transverse slide support pushes the Z axis stepper motor back into some form of alignment .
The packer is attached via one of the lower frame assembly holes using a M4 x 10mm bolt (see fixing image).
I have still used a 20% infill but increased the perimeters to 3. The print needs to be fairly robust but the relative compressive forces really depend on the tension of the X motor drive.
This is probably better installed before tensioning the x belt but can be easily retro fitted. I would recommend using better quality hex head bolts rather than the crappy cross head ones supplied in the assembly kit.
Collection of all my upgrades for the Zonestar at the following link: https://www.thingiverse.com/thing:2936870