I have no experience with Ross switches, and I only mention this as a possible last resort to look at. If your switches do not have a plastic cross-over plate in the middle of them, then kindly disregard.
I have had two Lionel 022 Switches, where the fixed plastic "frog" in the middle was slightly too tall. I know this sounds crazy, but when my cars, and one engine, ran through the switches, inbound on the curved section, the inside front wheels would hit that plastic frog and "rise up" just a hair, resulting in the front trucks derailing.
Were my switches level? Yes. I know this because I replaced these switches with other identical switches, and the trains rain fine.
I took a dremel tool, with a fine grit wheel, and very very gently ground down the interior flat section and rail section of the plastic frogs on the defective switches, just a tad. Then they worked fine. (The problem is that molded plastic frogs are sometimes not molded perfectly.)
Just maybe something to take a look at.