OK after getting to play with the sander more this weekend, I can say that it is not the conveyer, and it is not the sand paper itself, the paper is in pretty good condition, not burnt or clogged and I have excellent dust collection.
The house that holds the drum does seem to be vibrating alot under load. I can't tell if it is more then normal or not. There doesn't seem to be anything loose anything with excessive movement that would contribute to this. The connection there the drum connects to the motor does have a some rotational movement, but I think I remember that being there before.
So I'm stumped on this one. I'm out of sand paper but might try to change it out and see that that makes a difference. Even though the paper looks good, maybe it is just worn out.