Y axis help!

Im new to the x carve world, I just got my machine set up and working on the fine tuning. I having trouble with my y axis… my y axis will move smoothly but every 2 inches it runs into a rough patch. it won’t move the correct distance but after it clears that short gap it runs smooth again… any ideas would be much help!
even when I move the y axis manually you can feel rough patches as you move it the length of the axis. the motors are moving in the same direction, I retention the belt and v wheels but with no success…

Thank you!

Update! I fixed the issue, I loosened the bottom V wheels and that fixed the issue!