Either you're not explaining this correctly, or moskus is right - this takes the cake.
Are you saying the Track is visible when you start playback, but at some during playback it disappears? And then if you continue playback past that point, Track 2 will disappear?
Does it disappear from both the left and right side of the Track View? IOW, both the control section and the wave picture?
Or are you simply saying the waveform (picture of the wave) on the right side of the screen disappears. If so, this is somewhat normal behavior. If you stop the track and wait a second or two, the program will redraw the waveform. Waveforms are stored in a cache on your hard drive. When the cache gets full, HS2002 will overwrite older waveforms. In your case, this waveform may have been overwritten, and you just need to give HS2002 some time to recreate it.
If that's not it, we need some more details. Like, does it come back when you stop playback? Is it repeatable? Does it happen on just one project? Etc.