@brad would normally chip on on a topic like this, but he’s been rather quiet for the last few weeks. I think he’s busy working on the new user interface library for Cantabile, that’s a step towards having a MacOS version. Consequently he may be rather busy.
I would have thought you should expect the exact same behaviour for 32- and 64-bit Cantabile, so something does look wrong there, either in Cantabile or jBridge.
One further experiment you could do - try a 64-bit plugin on 64-bit Cantabile. If you see the same problems, then that would rule out jBridge, as that configuration wouldn’t be using jBridge.
Which state behaviour do you have “Export to parent song” enabled for? If it’s “Selected program”, then I would expect the program you chose in the menu to then be stored in the song. But if you loaded a preset from disk, Cantabile would still be saving the program number in the song, not the patch itself, and so I would expect that not to work as expected. However, why there’d be a difference between 32- and 64-bit Cantabile in that respect, I don’t know.
One more thing - do you see this on all plugins, or just a specific plugin? It could also potentially be a plugin bug…?