Bit cutting past corner (Moved)

Any suggestions on what i can check for this problem. The cuts are not real square and the bit is cutting past the corner where the bit starts and ends the cut. Disregard the uneven bottom. This is actually a scrabble board im trying to cut, the squares are about .75 and .15 deep. Tried two different bits 1/8 straight and a 1/8 downcut with a 1/4 shank, cutting 50ipm at .1 depth same result. My machine is pretty much stock. Any help would be appreciated.

It come from lack of rigidity and/or wheels / belts too loose or tight / cutting forces too high to counter mechanically.

I’m wondering if my y axis belt is a little loose. I’m going to tighten it a little and try it again

Too much slop. Tighten the ship.

Use a mechanical fish scale to tighten your belts. In the middle of the rail I believe its 4lbs at 1" pull.

yes ill try that