This has happened to me twice, where outside of a loco all you can hear is the sound that rings when you trip PZB for speeding. It first happened while sitting as a passenger in a Dosto at Coswig, and then again at Riesa while exploring on foot, as you can see in the video below. It goes away after a little bit, but I don’t know how. Playing on Xbox One S.
Turn off your safety systems when leaving a service to be a passenger. This has happened before on other routes.