This error still occurs and we as developers can not solve it. I reported this to Google support several weeks ago, but have not got any reply. I don’t understand why Google, which is such a creative and succesfull company do not fix this error. In-app billing works without problems for Apple and this issue could make customers and developers switch to iOS.
Google seem to have done some bugfixing, because the In-app billing errors don’t happen that often now, eventhough they sometimes still occur.
Customers still sometimes loose the upgrade to premium version after uninstalling the app and then installing again. I assume the best way of solving this is to store the purchases with “Android storage access framework” or Backuphelper. oswaldmandus, you mentioned Backuphelper. Would it also be possible to store the purchases with “Android storage access framework”?
You then mail them this license code after you have seen their complaints in the reviews?