Been using Studio One for a while and since the new BandLab release thought I play around with some tracks in Cakewalk. As you can see from this video, songs speeds up when clicking on different song positions, thought it maybe an Omnisphere ARP issue, but it happens to all tracks? Goes back to normal when you press stop then start again. 
 
 

Sorry but All I could see /hear was you starting and stoping the song. I didn't detect any speed differences unless your talking subtle. I couldn't see the Tempo read out, does that change? 
Possibly your Omnisphere is not following the tempo if this is what you are saying. 

Thanks for the reply, it's definitely not subtle. Here`s a better example. Tempo read out stays the same 105 BPM, seems to be an issue with Cakewalk not syncing to Omnisphere properly, doesn't do this in Studio One.

I had this sort of problem. One time, it wasn’t Sonar per se, more aligning i/o rates and letting Sonar share the sound device.

YMMV but i think it was due to Focusrite F/W drivers. I’ll do a search tomorrow, but from memory it was not a Sonar problem

Have you got certain events slowing the tempo down ?

BTW i am on an iPad so can’ see your specs.

Jerry

I wouldn't be surprised if this has something to do with Sonar communicating erroneous tempo and/or song position information to plugins when doing things like changing the playhead position during playback. Similar things can happen when enabling or disabling loops during playback. I can't work out from the audio exactly which elements of the track are speeding up and which aren't, but I can see that the Omnisphere arp is definitely speeding up. I would try to pinpoint exactly which tracks are speeding up and see if they're all either arp or sequencer based, because if that's the case then it's almost certainly Sonar confusing those plugins and making them thing the song tempo has changed.

I did post a better example 3rd post down and like I said it`s fine in studio one. Yeah, I've had the looping and going out of sync problem too! Not a lot I can do about, will just have to wait and see how BandLab fix longstanding issues bugs and future development in general. Thank for the replies :-)