I did some quick testing on the 64 bit version and it works better for me. There are some strange bugs in that build. Switching between presets under Web/DAB/HD, Analog Pleasure Deluxe is stable. Switching to Studio One, I get a GUI error and and warning about Sync I/O for sound cards which I have turned off. Things play normally for a few seconds then every filter past the noise gate stops working and goes black. Returning to Analog Pleasure Deluxe fixes everything. Other presets under Web/DAB/HD turn on MPX. I understand it is a test build.
This is indeed based on code that's very much "in flux" at the moment, the parameter architecture is being redesigned. I hadn't really tested it yet. Anyway, does your first remark, "I did some quick testing on the 64 bit version and it works better for me", mean that the PortAudio I/O issues appear to be resolved?