I'm experiencing an issue where the Sibelius Sounds are acting erratically when used in large band scores in conjunction with Kontakt 4 and VDL. Some of my wind instruments are loading and working fine, while others either:
1. Don't seem to load at all (no sound when I test them in the Mixer)
2. Do not play back if there are any articulations on the note
3. Work sometimes and don't work other times.

Specifically, the Alto Sax, Horn, and Trumpet instruments are having this problem.
It only seems to be a problem when I'm using them in conjunction with VDL. 

I have found some old threads about this, but no solutions.

You may want to consider adding some more instances of Kontakt in your active devices. The 16 channels can fill up rather quickly. You may want to add one or two more Kontakt instances and possibly another Sibelius Sounds instance in your Sound Configuration.

Any particular reason for not using Kontakt Player 5?