TS19 has a nice feature that marks routes that have a defect. Unfortunately TS19, like all Trainz products, refuses to allow the deletion of Unknown Assets from the asset lists of routes. Routes do not hold copies of assets. They merely have lists of stuff they may need so they can respond to the to the the instructions of the route's program. As such, while N3V rightly claims they know nothing about these assets, the routes know all about them.
Because the identification of Unknown Assets exists within the route the ability to remove Unknown Assets from the ROUTE should become available. Once that is available, if you see a marker for your route, you will be able to correct it with a route level deletion.
Because the identification of Unknown Assets exists within the route the ability to remove Unknown Assets from the ROUTE should become available. Once that is available, if you see a marker for your route, you will be able to correct it with a route level deletion.