As I remember there was another problem - with audio/video sync. The sound was delayed more and more - I've patched the plugin myself to disable the audio/video sync algorithm. But in last versions (I'm now using the 8649 version) it is ok. So it is maybe second reason of your problem.
You could test if immediately after switching to the channel the sync of subtitles is good or significantly better then after some time (1-2 minutes) it could be the sync problem.
Is there a CHANGELOG somewhere or something similar showing what's going on with the plugin development and the various revisions?