I decided to try the Synchron Prime demo yesterday, and getting that added the NKS installer to my "not installed" section in Vienna Assistant, along with an update to the NKS installer for BBO and Vienna Smart Orchestra.
Installing Synchron Prime went fine, but the NKS installers would invariably stall after the first installation reached 100% - all of the other installs in the same group would just sit at "Pending install" forever, so I had to force quit VA. I manually deleted my VSL NKS folder and tried a number of other things, but got the same issue every time.
I came here to see if this was a known issue with a fix, and happened upon a mention of VA hanging at the end of an install (https://forum.vsl.co.at/topic/61609/va-always-hangs-when-install-is-finished/1), but no real solution. Then I saw a topic about all NKS XML files getting wiped during install (https://forum.vsl.co.at/topic/61456/wiped-all-my-nks-xml-files/1), and decided to check my system. Sure enough, Komplete Kontrol no longer showed anything on startup - completely empty. Native Access also refused to do anything on startup - it didn't get to the point of trying to show what I have installed.
Poking around in Library files, I found the same issue as mentioned in the earlier NKS XML post - the Service Center folder (which contains the NKS XML files) in /Library/Application Support/Native Instruments had been turned into a 0 byte file that just opened Terminal. Fortunately, I have a nightly backup (as well as periodic off-site backups), so I was able to put the folder back in place from the backup. That got Komplete Kontrol back in business, though it had to rebuild its database. I had to remove/clean up after Native Access and reinstall it to get it back to functioning.
Piecing things together from those earlier posts (https://forum.vsl.co.at/topic/61569/nks-not-loading-on-macos-when-boot-volume-name-differs-from-macintosh-hd/1 may also be related here, as my boot drive is not named "Macintosh HD"), there appear to be bugs in the NKS installers that are causing installs to hang, and some sort of cleanup is triggered that, instead of only removing the VA-installed NKS XMLs, wipes the entire folder and nukes Komplete Kontrol and Native Access. Needless to say, this isn't great - I'm just a hobbyist, so my livelihood wasn't on the line, but it still involved a lot of hunting around over the course of yesterday, trying to figure out what was happening and then realizing that the issue was bigger than anticipated.