I just sanded a new installed red oak floor they had it installed we sanded it and we have chatter all though it and dark mark along the edges of a full edge area. We never had these problems before on the floors before this so I think the boards were not instaled right I could us some answers

Not being a sand guy.....I'd be real interested to know how installation could cause chatter. Sorry..but I kinda have my doubts. I have heard of sand guys sanding floors that were way out of flat, and/or wavy. Sounds like a PITA..but they get through it with no chatter. It makes sense to me that a loose/bouncy floor may cause chatter, ( but I would think the installer would notice that). The dark line almost makes me think equipment?

loose floors can cause chatter. Its normally old floors that have moved a bunch over the years, not new installs. Sounds more like equipment or operator more than the floor. Check the nail pattern out and your machine/paper.

Sounds like your sanding machine is the issue. It could simply be bad belts causing the chatter. When I had my Bona 10 inch machine, I would occasionally get chattering . I could tell right away because i could feel it in the handle. It was always the bad belt that cause it so I had to throw out about 1 belt from every box of paper I bought.

Other than paper, you could have a bad roller or drum tension spring on your machine.