Ok, thanks for the addittional information. We haven't been able to reproduce here, but will continue to try. Do you have any automation written for the plug-in in this project? Does this issue also happen if you try a realtime bounce in another session?
I understand the need to do a realtime bounce. In the meantime, as a workaround, you could print the track(s) using Tverb (either with an offline bounce, or by routing to a new track and recording the output), and then do the realtime bounce.