Wavy test cube Anet E10

UPDATE APRIL 2018 | I found that the issue is caused by the very cheap wheels. I fixed the problem by replacing the original wheels with some non-standard (a bit smaller) V-slot wheels using the original carriage. Unfortunately, those wheels are not on sale and I borrowed from a laser engraver, so you won't find them on AliExpress or other e-shop. You can buy some standard V-slot wheels, but because the diameter is larger you have to print a dedicated carriage or modify the original one (I prefer the last option). Check that your new V-slot wheels are not cracked or have any other imperfection, because it would mirror on the print.

Printing a 30mm cube in vase mode (sliced with both Simplify3D and Cura) with the Anet E10, the X faces come wavy. Y faces are perfect. Every screw is tightened and I don't know how to fix the issue.

VIDEO FROM EVERY SIDE - https://www.youtube.com/watch?v=ga_VY77UnPI

NOTES
- I attached the STL file of the cube (it's a 20mm cube, simply scale it to