Hello DG,
No, I never play while loading sounds. I always wait for them to load fully and then I start playing.
The thing is that this problem does not seem to be a real problem, but more of a bug. And this is because as I already mentioned it disappears after playing with the instrument for a while or after unloading and reloading the instrument.
To be honest, it reminds me of a problem that has been discussed in the forums a while ago, where you loaded a patch, and all your notes clicked the first time you played them, until you have played them all once at least.
For example, you loaded a Bosendorfer piano patch and in the begginning , every note clicked , but once you played once the notes of the patch the problem was going away. I remember many users had that problem back then. I used to have it too, but I believe this was solved after an update in Vienna Instruments (Pro was not even released back then).