When SONAR (or Acid Pro, for that matter) guesses loop length, it will sometimes do double or half time. The tipoff is that the number of beats is not correct, which requires editing the Beats field in the LCW. Depending on the loop, you will run into this problem at some point in the future (if you haven't already, then consider yourself lucky

).
This version of SONAR fixed a bug in the Loop Construction window; it now allows the cursor in the LCW to track loops properly when you're zoomed in to where you can't see the entire loop in the window. This may make the phenomenon described above more likely, however I have not experienced problems with loop
playback using 2016.05. What happens above comes into play only when creating a Groove Clip. Entering the correct number of beats fixes it.