The plan.at import in Austria messed up lots of things. I cleaned up some streets in Achenkirch for which I made the GPS tracks myself. Besides, I'm regularly there, so I have a fairly good knowledge of the area.
Then I corrected the B 181 Achenseestraße (and no matter what it says elsewhere, according to the offical highway law, it's not Achensee Straße) on its whole length. Should be fine now.