Cutting quality problem

Hello,
I’ve just noticed a problem with the cutting process; the cuts aren’t square and the joints are very poor.
How can I resolve this issue?

Are the belts extremely loose? If you wiggle the laser head lightly, does anything feel loose? How does it look in the preview, is that file actually really square?

I’ve already tightened the belts. The file is really square, but the problem is with the drawing because the misalignment is on the vertical axis.

I didn’t feel anything when I moved my head manually.