First; Make sure you followed this link to see if you miss something.
Second; check to see if your wheel spacers are installed correctly, maybe V surfaces are not sitting to maker slide correctly.
Third; turn your machine off, bring your X axis all the way to the edge which you think it's getting tighter. Loose four screws holding maker slides, check your V Wheels if they're free to spin. Tight those screws back again, adjust your wheels evenly (small amount per eccentric at a time).
Now push your X axis to center, are your wheels getting looser ?, then you need stiffness mode to make two maker slide straight enough.
The X axis movement is very important for circles and arcs.
Making belt tensions too tight doesn't give you anything but problems. Just needs to be tight enough not to jump teeth, and Y axis belts must be even on both side.