shown error on OSMI ““error_over_rail”

Does somebody know why there is some shown error "error_over_rail" on OSM-Inspector for ptv2-busroutes? Concerning the title you could believe the ptv2 busroute-relation has some members which are no "highways", but some "railways".

I took a look on the members, but i can´t find any mistake.

Here are some examples shown error "error_over_rail" on OSMI through Austria:

• ptv2-busroute Flixbus N538: Florenz, Villa Constanza => Prag, ÚAN Florenc
• Flixbus N952: Frankfurt (Main) Hbf => Vukovar, Busbahnhof