This all sounds weird in my ears, that the Kontakt.vst should cause a problem. Kontakt has different “flavours” of the plug-in because they offer different output configurations, i.e. stereo out, 8 and 16 individual outs. Don’t know really for what purpose, most likely the stereo out uses a little less CPU than the multi out. By default we have only the Kontakt 16out whitelisted, because that is what we assume the users most likely want to have, so that they can tweak the sound of individual instruments in the Dorico mixer.
Have you edited the whitelist and also activated Kontakt and Kontakt 8out?
That what user Estigy mentions is a good point. It could happen that upon loading a plug-in is throwing some notification or error message and is waiting for a prompt, and that the notification window is not visible because it is hidden behind the Dorico window. When loading is stuck at 60%, please try and move the Dorico window to the side or minimize it to see if there is maybe something hidden behind.