Don’t worry, surely no issue 
I’d love to get in touch with the Italians - kind regards to them if possible, please
I’d like to add here that in the case of my Belgian friend his drive was replaced two times by an official German Strida dealer, where the bike was bought, on warranty without problem.
(German because my friend lives exactly in the border triangle of Germany/Belgium/Netherlands near Aachen 
)
It will be hard to find out reliable number for a rate; guess Ming cycle won’t tell us, Strida dealers might watch things from a different angle of sight (partially of course comprehensible) and here at the forum will be just a minority of all Strida owners.
Well…and at forums appear people often if there’s a problem - and not if everything is running fine, I’m afraid of…
What I mean is; none of above mentioned parties will be able to supply true data!
But as always; there must be at least one exception to substantiate the theory;
for my meaning should this be the factory of the drives, namely sturmey-archer.
(I’ve heard that all defective drives will be sent back to Sun Race for refurbishing - they must know the real rate.)
So…what’s more easy than just writing them and ask?
Would you think that’s foolish?
I can tell you - I did!
Of course I got no reply at all 
Also naturally I’ve asked directly in Taiwan and Korea about “how many” and everybody said “a few”…