Strange line across my prints 4800 stylus pro

[Phil Vanderloo]

I'm using 17" roll paper. Canson Baryta photographique. I'm getting a weird horizontal dashed line right across the middle of my print that looks almost like a pinch mark. It's a perfectly straight, very uniformed dashed line.
It's happened on my last 2 prints.
Other than platen gap issues, which doesn't seem like it would make just one line, I can't imagine what to look for. Any advice?
Thank You.