Confirmed, changing my audio settings solved the VST path sticking problem after completely deleting the VSTAudioEngine3_64 folder. Thank you!
Kontakt still not available unfortunately.
I’ve now bee testing with no whitelist at all, but the problem persists. For what it’s worth, Kontakt gets put onto the blacklist immediately after clicking “OK” in the VST2 paths dialog, no program restart required (but I still tested this anyway). My next test is to completely remove Dorico 3 and reinstall.