As I said in my first post, the latest version of Solina V2 did initially work in Logic.
It was only after I had to force quit Logic that this problem arose, and for some reason it now also affects the latest version of Vox Continental V2.
Yes, it is an audio unit issue, but I suspect that some file or files, possibly an Arturia file(s) that is used by all Arturia audio units, has become corrupted after I forced quit Logic.
I've tried whatever Logic fixes that I could think of including trashing the cache file com.apple.audiounits.cache, but still the same problem.