Adding some Kontakt vsti's freezing GUI and hanging Sonar in 2016-05 [FIXED]

Hi folks.
 
I had my first issue with Sonar in a very long time last night. I was working on a project with around 10 vsti's, including Superior Drummer,  Drumazon, Mpower synth and multiple instances of Sylenth. After upgrading to early release 2016 - 05, I was attempting to add an instance of Kontakt containing Electri6ity. The synth would load and could be played from my keyboard, however a few seconds after playback was started the GUI would freeze. The song would continue to play until the end. It could not be stopped using any control surface, and if I clicked anywhere on the Sonar interface I got the dreaded spinning circle, followed by the white app hang with notification. As I mentioned, through all of this, the song would play through until the end. It seemed that only the GUI was freezing.
 
I experimented with several other Kontakt libraries. Some caused a similar freeze, whilst others did not. Unfortunately  I did not have a lot of time to trooubleshoot. I had made an acronis system backup before installing the latest update, so I restored my system to 2016-04. Using the versions of the project that I had saved in 2016-05, the problem persisted. However, once I resaved the project using 2016-04, the problem disappeared and all of the synths worked as expected.
 
This could of course just be one of those weird issues that pops up in a single errant file now and then that coincidentally occurred after the update. Just thought I would check whether anyone else had issues before I give 2016-05 another run.
 
Thanks:)