I have a Performax 16/32 sander. Recently I sanded a oak top 2' x 5' with it. I have home made in-feed and out feed tables for it. I suspect the pressure rollers for it are too loose. I ended up with some very faint marks left by the drum, almost like snipe but at random intervals. My habit is to put pressure down on the piece with my hands as it passes through. Perhaps these marks are left when I move my hands, as if the piece rises slightly for an instant. I remember trying to adjust the rollers several years ago, but think I gave up on getting them just right. I also think these marks have sanded out of other pieces because I finish up with a ROS, but the oak is hard enough that the ROS did not get it all.
I read the manual, but it basically says they have to be properly adjusted. Also went to the Jet site and Youtube looking for a set up video but did not find anything useful. Do the rollers in yours press down firmly? Do you have anyway to convey how firmly? Any suggestion?