We also rolled back to plugin.google.iap.v3 because with iap.billing we had a few complaints from customers that the app did not recognize their purchase, thus blocking access to their purchased content.
We have no idea what may cause this problem and we are unable to reproduce it on our own devices. Our app is a simple try-before-you-buy freemium app offering a single in-app purchase to unlock the full content.
Has anyone else switched to plugin.google.iap.billing? Anyone wants to share their experience?