Thanks Gysbert, I didn't expect any answers already.
Doesn't look like this. I've changed geocoding from Google to mapquest, and it works this way. It is slower, but I don't expect more than a few addresses per reload. So, the problem has been fixed for the client.
Still, it bothers me. I thought that maybe Google blocked the requests, because a few weeks ago the app was sending hundreds of requests with the blank addresses and possibly extended Google limit - but why only for QVB and not for Desktop?