Image should be self-explanatory
(http://i.imgur.com/CocgzcA.png)
The whole track vanishing seems to prefer to happen with eleveated monorail, but I can confirm the track showing in front of the depot and station also happens with ground track.
I'm running simutrans 112.1 - r6212 with pak128 2.2.0.
This bug still exists with Simutrans 112.3 (release version) and Pak128 2.3.0.
It happens only from time to time. I think that it happens more often if the game is paused but this could also be a false impression.
With Simutrans RC 120 and pak128 2.3.0, this glitch happens only on fast forward, so it seems to be partly fixed.