The change log reports: "Bug fix for creating new tasks while the sync with Google Tasks is running"
Now, it's clear why it happens just one time every N tasks creation, with N quite big!!!
It's hard to test it because it happens only when sync is running. Anyway, I can say that until now, after 10 tries, I had no problem. Let's see next weeks.
Thank you to MultiFilas for the nice idea and to you.
Bye
Giacomo