Don't mean to bump up an old thread, but I'm having a similar issue with Edinburgh - Aberdeen. It tends to stick, but after a minute or two, it works properly again until the it sticks again. This is only a visual problem, the sound doesn't seem to be effected by this.
Also, maybe this isn't an error, but when I'm closer to Aberdeen than Edinburgh using the HST timetable, I pass a 158 at a station. When I'm about thirty seconds away from this 158, it's horn goes off and I can still hear it as loud as if it was next to me. It's a bit odd.