Not sure what is causing this...but recently, seemingly regardless of how many tracks (3 or 30) or whether or not any plugins are being used....if I'm using the "loop on" control to practice a part...I get MAJOR stuttering..it might play through the section once ok, and then continually stutter through 2 times and maybe play another one ok.
 
Nothing in my system has changed other than Sonar updates and Win10 updates. 
 
Anyone else notice this?  I was using the November update....and tried going to the December early release to see if that helped....it didn't help. 
 
 

I heard someone else mention this earlier today. not sure if its a global issue or just random.
I would check your Roland / Devices buffer rate. make sure the new update, or windows update didn't reset some defaults within Sonar.

Thanks Chuck...I'm cautiously optimistic that indeed that was the problem.  I honestly don't remember what everything had been set at...but after experimenting with the driver settings a bit.....it would seem that the problem has resolved itself!