I've run into a VEP6 problem recently with Kontakt 6. Latest updates on both. If I load my metaframe, my template, frequently the first instance - and sometimes the second - will load empty. It's saved with stuff in it (usually Spitfire patches)....but loading it up, boom, the Kontakt instance is empty and remains empty even if I try and reload the same metaframe.
Same thing is happening over three different slaves. Each instance is fairly full, but there's plenty of RAM and sometimes it seems to work fine, I'll save and reload and it'll reload just fine. Then at some point...it just won't. Other Kontakt instances within the same instance in VEPRO load fine. It's mostly typical of Spitfire samples but not exclusively so.