Tic Tac Toe Board Help

Why is the top right corner cut out a little bit more on each square?

The bottom of the pockets indicate you need to tram your spindle or something is loose.
Something loose (v wheels, possibly belts) could cause the upper corner issue.

Your machine isnt rigid enough or bit not sharp enough for the feed and speed you are carving with.
The bit deflects a little when going X/Y but when it plunge (Z) there is “no” sideway force applied to it.

Too bad Easel doesn’t support ‘ramping’ when plunging into material.