Hi Bob - I believe (believe because I haven't been able to reproduce it) I have a fix for this in 5.0.16 that's been in beta for a while. Best I can tell is that google doesn't always respond immediately to confirm the license so I've added a grace period to wait for an updated response. It seems to be stable so I've promoted it, it should be available on play within a day or two.
If you're already running that version please try to capture the log when it happens and send it to me, I'll see if there's something else going on.