As a preface this setup has been working on the same device model (CRS326-24G-2S+) running version 7.5 for several months. The instance with the problem is on 7.7.
The mangle rule is simple prerouting single src address protocol tcp port 80.
Action is route to a route dst which is in the routing table. The mangle rule is processing packets and logging so the rule is being hit. Problem is the route destination is not changed to the entered value.
Any thoughts as to what would cause the route dst to not apply?