Originally Posted by
Briareos
Well, the bike is practically in mint condition so I doubt chain wear or RD breakage is the problem.
Since it's 1st Gen. Rival (silver) it has to be the trim right? The new Rival has the trim feature that only Force/Red had previously.
Yes, it could be trim, which in high gear is actually determined by the limit screw. Adjusting the cable lenght would change trim in all the other gears, but in high the cable is slack and the RD rests on the limit. But if it's an RD issue that would argue that it would skip on this sprocket with both chainrings, not just the inner.