What to do if the edges are not straight when cutting acrylic?

Hi guys,
From the picture you can see that the cut is not straight along the Y axis but the cut along the X axis is straight! Not sure how the fix because if it was the lens focus issue the cut along the X axis wouldn’t be straight as well, right?
I’m using a 2" lens, 90w CO2 laser , the material I’m cutting it’s a 5mm acrylic
Any help would be much appreciated.
Cheers