I have a 2005 25B21FB
Bigfoot model, and was aware of the issue as well. I tow with a 2007 Toyota 4Runner, and a WDH, and have no problems. If you are mindful of how the trailer is loaded and have a good TV, it's fine.
The issue seemed to crop up if you had the wrong combination of items (empty fresh water, full black tank, empty propane, poorly loaded trailer, and so forth, IIRC) that it *could* be prone to sway.
Very sturdy, well built trailers IMO.
Good luck with the sale.