This isn't a bug so much as a matter of poor interface design, which would however be a) I think quite an easy fix and b) enormously helpful to players who feel overwhelmed by PZB, especially when they get surprised by a required-response signal they weren't expecting. The issue is simply this: the HUD's 'next signal' display renders German green/yellow signals as green. This is HUGELY misleading; a green/yellow means pretty much what a UK double-yellow does, and is most definitely a caution, not a clear. The HUD indicator ought to be yellow.