I reduced the price and added a warning about how rubbish this library is technically (especially with caching, memory use and stability). It seems like it's getting worse, not better. I didn't do anything wrong with this sound set, the crapness is purely down to Spitfire (mostly) and Sibelius (a little).
On the up-side, Sibelius's latest version doesn't corrupt the house styles any more when you use my script to import more than one of them.
Quick note: my developer certificates expired, I don't have a (Virtual) Mac any more, and lack of support from the community (and the industry) means I'm an IT contractor again and thus not supporting any of these things.