I strongly think Steinberg should implement a time-out in their VST3 checking software if this is still happening (to be it was happening in Cubase 11 but not 12). Because it seems bizarre that if there is an issue with one plugin the whole software stops working.
In my case the problem seemed to be with a Rhodes plug-in (V-Pan).
For people coming over this feed the way I discovered it was to go in the Common Files/VST3 folder, take out everything and save it in a different folder and slowly introduce things, open Cubase, close it, introduce more VST3, repeat. To fasten things up I put things back alphabetically… That’s how I found the problem was with a plug-in that began with V, and then for those ones I did the operation one by one until I found that the issue was with V-Pan (lucky for me I only had 2 plugins starting with V).
The fact is that if there is an issue with a VST2, Cubase puts it in the blacklist and keeps going… why it doesn’t do the same for VST3 plug-ins is beyond me, but you would expect it to happen from a top producer like Steinberg… Error handling and time-out is coding 101 to not get software stuck.