Yep, it's a bug.
The best way to eliminate it is use the "call out" option. You have to configure your mobile phone not to require a password when you call in to GV to place a call, but other than that it works like a charm.
It was frustrating the hell out of me, as it appears, if you don't actually connect (VM or live person) in the call using the callback option, it'll keep retrying the number until you do.