As the title suggests, this can especially be seen looking at the fixed V-Wheels at the top.
If you rest the right side V-Wheel on the rail, the left V-Wheel wont sit down on the left rail properly and therefore it creates a problem when trying to adjust the eccentric nuts when the V-Wheels are not lining up with the rails properly.
Its as though the washers on one side should be SLIGHTLY bigger in order to offset the V-Wheel enough to line up properly.
I’ve assembled a fair number of these machines and this has been a frequent issue. If i had time i would buy slightly thicker washers and file them down to the perfect size but that takes a long time. I did this one time and the X-Axis ran smooth as butter and was solid.
If i don’t modify the washer sizes to get all the V-Wheels to line up perfectly then I have to leave all the eccentric nuts in the open position otherwise trying to tighten them causes issues with the X-Axis. (e.g. One or more of the V-Wheels are under strain at a weird angle from not sitting properly on the rail causing them to slightly warp making the movement of the X-Axis to be very rough.)
These pictures are upside down for some reason, but the bottom is the top of the X-Gantry.
Left Side Bad Fit:
Right Side Perfect Fit:
TL;DR
You have to get thicker washers and shave them down to the perfect spacing on one side to get all the V-Wheels to line up perfectly.