Hi M!
I moved your post to the relevant forum, where hopefully you will receive more replies.
Welcome to the G!
How are you chopping, and what kind of moulding is it?
With a chopper, you have to take “bites”, you can’t cut through it all at once. Some moulding might require more and smaller bites than others.
The moulding might also be the issue as a lot of gessoed moulding doesn’t chop well on a chopper.
If the blades are new, I assume that is not the issue. Blades need to be sharp of course.