I'm experience a strange issue where the sound being loaded for a given instrument does not match the instrument. This happens primarily while writing aux. percussion parts that feature many instrument changes. Here's the steps that usually occur.

1. Write a line in a rack percussion staff for Instrument X
2. Do an instrument change to Instrument Y, correct sound loads
3. After about 10 seconds of working with instrument Y, Kontakt 4 appears to switch back to Instrument X
4. I go and look in Kontakt Player and there are now two instances of Instrument X. However, only one specific sound from Instrument X will be available.

Example: I'm using the Abel 6"; triangle instrument. I go to switch to Treeworks Double Row, which works initially, but after 10 seconds I see the triangle sound load again. After that, the only sound I can get from the area of my staff that SHOULD be wind chimes is the triangle roll sound.

Ways I have unsuccessfully attempted to troubleshoot:

1. Manually loading the sound (Instrument Y) I want back into Kontakt. (Can't seem to get the part in the staff to ";find"; that sound)
2. Deleting one or both instances of Instrument X.
3. Deleting and re-writing the entire area of the staff.
4. Deleting that instance of Kontakt in my Playback Devices, loading up a new instance, re-loading all of the sounds into a brand new instance.
5. Starting an entirely new staff and rewriting the entire part. This works sometimes, but sometimes the issue crops up again on the new part!
6. Making sure that that particular instance of Kontakt was not full (that was the issue...once.)

Anyone else have this issue? I wonder if it might even be a Write Score issue...but it seems that the template knows which instrument to load, but then something is forcing it to switch back to a previous instrument.

Info:
Sibelius 7.5
Kontakt 4
VDL 2.5.5
Mac OS X El Capitan 10.11.6
16 GB RAM

Thanks!

Sounds like a case of not having enough instances of VDL in your Playback Configuration. Add one, or two, and hit play.