Just to clarify that the problem was not quite as simple as the sustain pedal not working - sustain does work in X3. The problem was for a specific workflow when you record over existing data that had sustain pedal events then there is the potential for multiple sustain events to be received in a random order for a *single* note event. This is the specific area that was not handled properly and it could lead to stuck notes. The issue existed in all prior versions but was somewhat more noticeable in X3 due to some other unrelated improvements.
 
The fix was far from simple and involved implementing new functionality for managing MIDI event reference counting inside the DAW. Prior prior versions of SONAR never implemented this so one could argue that this was not a bug but a limitation of the earlier versions. BTW there was indeed also a simple bug that compounded the problem. There were certain MIDI CC's that were being mistakenly treated as pedal events and could turn off a pedal at the wrong time if present.
 
PS: Please also check your PM for some more info...

The main reason it was likely not fixed in X3, is because I seemed to be the main person shining a light on this problem and my bug report didn't get to them until after the last bug fix X3e. I was very late in the game with upgrading to X3. I had problems with Win 7 and my sound card that took me a long time to resolve.
 
I upgraded to X3 a few months after I got Win 7 and 8.5 working well. Cakewalk was already working on Platinum by the time they had a clear understanding of this problem after I put together a good recipe for demonstrating this. Noel assured me it would be fixed in Platinum and I thought that was reasonable considering the situation.
 
This is one good reason why this new system is the Cakewalk Subscription service is good, because they are always implementing fixes instead of shutting them down to work on a new big version.