Problem: Render to WAV makes Real Drums continue after song ends.

Details: My song has 3 real tracks: piano, bass and drums. It plays correctly in biab (i.e., no extra drums after the end of the song). However, when I render it to a WAV file, I get an extra 2 measures of drums after the song ends. The song has a tag ending with shots, the last chord is held. Biab is NOT generating its own ending. I've tried muting the drums after the last chord, no joy. Any ideas how to solve this? Thanks!