Several Kontakt libraries fail to load their GUI's correctly inside Ensemble Pro 6. A previous post mentioned CineSymphony Lite, but I can confirm it effects the entire line of CineSample's orchrestral libraries and Output Sounds: Signal, Exhale and Substance libraries.
The fact that it effects libraries from different manufactures means it is highly likely other libraries are effected, but these are the ones I own that I can confirm. I am sure its Vienna Ensemble Pro 6 that causes it, as loading it in the DAW and Kontakt standalone does not produce these graphical glitches. I recall having used these libraries in Version 5 without these issues making me more certain its exclusive to 6.
These graphical glitches render the libraries absolutely unusable. The problem is compounded by the fact that It seems to inflict newer libraries, making this a HUGE issue as Kontakt is a popular platform with more and more libraries being added as well as older libraries being updated with new GUI/Scripts.
Using latest version as of this post.