Ok, so I ran one of my recorded tests on both versions 2015.2.723.0 and 2015.3.1112.0, and again the newest version fails in detecting the Rad ribbon tab objects. Actually it doesn't fail, I eventually have to stop the test manually, but it stays on that test step, looking for the object.
I've attached the two log files, hope that helps you in investigating this. Also I've asked my developers to create an application mock-up and I'll send that to you as soon as I have it.
Note: After many attempts I've noticed that occasionally the test does run, but this is in no way consistent. More often than not, it will fail, as per the attached log.