In the meantime, I tried several VST wrappers, I ended with:
https://www.bluecataudio.com/Products/Product_PatchWork
This seems to do the job (and much more…). The first of the other two that I tested, had a really horrible UI, and the second cutted of the release of some notes. These both were useless to me.
Of course, a real solution of the problem would be nice, but now, that I have the blue cat… I am happy so far.
The support call at NI is still open, perhaps I get some useful information from there. If so, I let you know.