MIDI Dropping Half A Tone randomly

This is really odd.......I'll see if I can explain it properly.
Subsequent to a Windows 10 update, all sorts of things went tits up on my Sonar X3 Producer so I thought, "why not upgrade to Sonar Platinum" as I was planning to do that later this year anyway, mainly for the multi-mix function.
 
Anyway, having done the upgrade I had a few immediate issues which were all swiftly resolved by a support call to Cakewalk - cheers guys, you were brilliant, but I now find that Soft Synths and MIDI controlled external devices (Roland JV-1010) are randomly dropping half a tone during recording or playing. This occurs with two controllers - an Alesisi Q49 keyboard and a Roland GR-55 Guitar Synth (although not on the GR-55 audio obviously) as well as during playback of soft synth and MIDI controlled tracks. I assume from this that, as the problem is global, it rules out the MIDI controllers as cause and because it also occurs during playback of soft synth and MIDI controlled tracks that it must be something to do with the relationship between SONAR Platinum and Windows 10 (64-bit) Version 1607 build 14393.321.
 
Anybody had the same problem and if so got any ideas how to fix it?

"Dropping half a tone?"
 
 
Does that mean that the pitch of a note (or a portion of the note) is lowered by a half tone? If so does the next note occur on the correct pitch or do subsequent notes stay low until the next event? Does the MIDI (the actual note number as opposed to the audible pitch produced by your unspecified synthesizer) show up lower?
 
Does it mean that half of the duration of a note is not played? Or that some notes are not played?
 
Does it mean that... never mind. I have no idea what you are talking about. 
 
Why not start over and describe in some detail what is actually happening?

So if the MIDI note number is not changing, and the perceived pitch is changing by a half tone lower, the most likely cause is that you are experiencing a change in the sampling rate from 48 kHz to 44.1 kHz. If so you should also have a slightly slower playing of the recording, but that may be harder to perceive. The fact that it changes unexpectedly suggests that another application on your computer is taking control  of the sampling rate of your interface so that the interface is using a different sampling rate than Sonar. 

When I read the title first thing comes to mind is a controller sending a pitch bend. This can happen as Bob has said even if you don't think you've moved it. They can go wonky.
Craig's advice on disconnecting all controlers is your best bet.
And if that  doesn't stop it then yes, look in your event list.
I doubt if it is a sample rate issue that's just not possible mid song without things crashing to a halt, and Sonar will warn you anyways when that happens.
 

I noticed you have a V-Studio 100. IIRC the 8.1 drivers don't work with Windows 10; you have to modify the .INF file.
Try to borrow an ASIO interface. Set a System Restore point, install the interface's drivers, and use that for a while to see if it fixes the problem. It's sounding more and more like something hardware-related; software doesn't just decide to change pitch, and given that this particular problem has not been reported by others, it's likely system-specific.

Sorry for the delay in responding. I've been fishing!
 
I'll give all your ideas a go and see if they fix things. Regarding the Win10 drivers. I've no idea which ones are being used as the VS-100 updates itself according to Cakewalk/Roland but it's interesting to note that it worked fine with Win 10 for several months until the most recent O/S updates. It's a bummer because everything else is working just right and Platinum seems like a smashing product, particularly the Mix Recall.

Without wishing to tempt fate, I've disconnected the Alesis Q49 controller and things seem to have stabilized without it's contribution. It must be an issue between it and the latest Win10 updates. Perhaps Alesis haven't caught up yet (or don't plan to for this model). At least it's a relatively inexpensive item to replace if push comes to shove!