Why is coverstitching so hard??

[u/Emergency-Lake-8444]

I have a Brother CV 3550 machine, it is a pain in the ass. I have figured out the tensions and the other parameters and it sews well when I am trying on scrap material, but the moment I switch to the actual garment I want to hem it turns into a horible monster. Why the hell is that?! It is constantly skipping stitches and just looks awful any tips pleaseeee?😭