I'm a little puzzled by how it is cutting. The inner rectangle is clean and neat and it just seems to be that one section of the file where the problem is. I looked at the file and don't see any major issues with it but will try to cut it tomorrow out of the thickest chipboard I have and will report back. I do wonder if the blade is protruding a bit too much and/or there is too much force because of the movement in the cutting. I wonder if the blade is catching and dragging a bit. It almost looks like the blade may be chipped, except the inner part is cutting clean. I would still check the blade and would definitely be sure the blade is not extending too much and/or is not cutting into the mat.
I would definitely slow down the speed and see if that makes a difference. I usually cut most things at a high speed (750) - but when I have cut issues, the first thing I do is reduce the speed and that often solves the problem.
Do double check the blade and how far it is out, be sure it is not nicked, use the setting tool and slow things down and see if that helps.
If it is humid where you are, that could also cause issues especially with materials like chipboard. Humidity can make the best material next to impossible to cut. Just one more thing to consider.... (or if the material has been exposed to humidity even if it isn't humid right now).
Hang in there- you will get it!