De-installed VST Live, dowloaded and installed version 1.0.41 and did exactly as you described. Switching Parts will switch sound from distorted to clean with delay, no matter if switched manually, or by transport trigger. Are you sure you are really using the latest version? Go to Help/About and check top left should say 1.0.41.600.
I also used an Octavider and Flanger in Part 1 and clean plus short reverb in the other to make it even more obvious. It clearly switches and no residuals from the other Part. If you still think that it is wrong, pls send me a simple project.