Soft Synth Instrument and MIDI question

I have a bass guitar MIDI track and I inserted BASiS as the synth for the track. The first 8 measures or so play fine. But after that the bass guitar sound slowly fades to zero. I watch the volume control on BASiS, and it slowly moves to zero. After a few more measures, the sound will come back up slightly then drop to zero again. The track and synth are solo'd. The MIDI information looks as if it is being constantly read because I see the meter on the MIDI track moving. My CPU usage only hits about 10%-15% during this time. I have checked the event list for this track and deleted wheel and control events, and I can't find any other events (after touch, etc) listed. BASiS doesn't do this in the other MIDIs that I have. I have tried to make a new bass MIDI track by inserting a new MIDI track and manually placing new notes in the new track, but I have the same results. Is there some sort of "global" or hidden event that I'm missing? And yes, the software that I have is 100% original and registered.

I watch the volume control on BASiS, and it slowly moves to zero.

If there are no CC7 Volume controller events in the MIDI track (and not on some other track or layer also pointing at BASiS), the only other thing that could cause that would be a MIDI volume envelope on the track, or on some other track also pointing at BASiS.
If you're not set to show unselected, "ghosted" automation envelopes, you might not see it (View >Display > Display Ghosted Data in the track view menu). And if you go to Automation in the Edit Filter drop-down, you'll see a color next to any automation envelopes that are active.

EDIT: If it's a Simple Instrument track, you'll need to split it to separate MIDI and Audio tracks to get to the Edit Filter for the MIDI track.

EDIT 2: Dang. Forgot I was in the pre-X1 forum. So Edit Filter and Display Ghosted Data are not applicable.

I archived all the tracks except for the bass track and inserted BASiS as the synth for the track, and it worked fine. I think I my have had something or some other track also pointing at BASiS, just as brundlefly suggested. I just sort of panicked, something I don't normally do. Thanks for the help everyone.