If you bought a GEEETech Prusa i3X kit and got the PCS8UU linear bearing models, there's a chance that acrylic parts:

I3B1-23 (A23 in the youtube videos)
I3B1-16 (A16 in the youtube videos)

have only 4, misaligned screw holes for the bearings. If that's the case, then you got the acrylic parts suitable for the older SCS8UU linear bearings.

Re-drilling the existing holes and making new ones is an option, asking for replacement parts is another (a fix to their original mistake that comes with a fee on their part, oddly enough) and the third option, which is to print these replacement parts instead.

These parts were produced by measuring the shipped, incorrect ones and setting the bearing holes properly.

I used blender to make the models and later on, netfabb to correct them, before printing. PLA works fine, ABS should work as well.

Printer:

CTC 3D Dual Extruder

Rafts:

No

Supports:

No

Resolution:

200 micron

Infill:

25%