I have both synths but am swamped at work and doing some long needed learning on X3/songwriting so haven't used either synth yet as they're still 32 bit.  However, you should let the company know as they've been pretty responsive to a couple emails I sent to them.... they're supposidly working hard on 64bit and I hope they improve the browser...
 
I've flagged this thread and will post thoughts as I have time.
 
best of luck, guys.
 

I just sent SonicProjects an email with all the info I've collected. Hopefully they can come back with something useful. I'm also in the process of sending something to Cakewalk.

I heard back from SonicProjects and have been exchanging information. This is what he's theorizing:
 

This sounds to me as if it could have to do something with how the Sonar bridge handles fxp/fxb chunks. The prerset system of OP-X PRO-II is entirely fxp/fxb based. Most sequencers save the project with a complete fxb chunk (so the temporary version of a full fxb bank including all changes, with the last chose preset as default). It's possible than the Sonar bridge somehow handles this differently, maybe there's somewhere a setting for it.

 
He asked for some more data that I sent him, so I'm hoping that he may be able to come up with a fix (or at least a functional workaround).

Hey Jeebus, I just wanted to say that I use JBridge and my OP-X II Pro saves and edits load just fine. So I would say the SonicProjects guy is onto something.