unreliable horizontal movement

I have been working with my MPCNC for a few months. everything seemed to be running ok so I started cutting some simple shapes. I am finding that parts are ending up thinner in the Y dimension than they should be, X seems better and Z seems about right. I am also finding that it seems to be cutting some corners and angles short.

In trying to trouble shoot I checked for play in various parts to see if that was at issue. I am not finding much play but I do find that when not moving one of the x and one of the y motors seem engaged and holding their position while one for each axis seems to move freely from the position it was moved to. The motors are turning but should all four motors be holding their position and resist movement?

Take all the belts off and make sure each moves and holds as it should.

Check the pulleys while the belts are off.

If that seems right a picture of everything or a lot more details are needed.

Wow thanks for the fast reply. I actually think I found it just after posting. The hex screws holding the gear on one of the Y motors had come loose. I will have to try to cut again tomorrow. thanks again.