What sort of instability are you experiencing?
I have - and have had with X3e as well - on-going instability issues with the Quad and Plt. Initially after the Kontact 5 update, things were a whole lot worse and I could not work on any project in Plt, so I went back to X3, which has been reasonable stable for a few weeks. I've recently returned to Plt, and apart from some 'exits' from closing some projects only - and again Plt not finding the drivers on the system and having to unplug/repower the Quad - it's been an 'okay' experience...but I'm not holding my breath at this point.
I've contacted Roland Support on quite a few occasions, trying to get to the bottom of these issues with Sonar and the Quad, but to no avail...apart from some various ideas tried, nothing has changed. I'm reassured though from Roland that they have developed very 'robust' drivers...hmm. Nobody ever seems to take responsibility for crashes, stop workings, audio interface dropouts, poor 3rd party interaction with DAW blah blah. In the end, I develop work-arounds and/or let it go for while. Strangely, there are days when things seems to be going well and then I'm back to dealing with issues that just gets in the way of making music. Even sending an error report to Cakewalk following a Plt crash doesn't work here as well. Part 'n parcel!
I do enjoy while it lasts though.