Vermeer mc4500

I have a Vermeer mc4500 that I’m having trouble getting it to cut alfalfa. Sometimes it will cut fine but at times it will leave a strip of uncut alfalfa. Seems like it is almost always in the side swing away from the tractor. The field is pretty rough. I’ve tried different speeds and rpms and still can’t get it to work right. Any tips on what might make it cut better? I’m fairly new to the disc mower world. I’ve ran sickle mowers for years and so far have not been super happy with the disc mower.

Vermeer mc4500