I am working with auto-renewable subscriptions. When the app has successfully finished a transaction, it sends the receipt to our server to validate it and to check that the last transaction identifier exists in the receipt.
From time to time, our server returns an error saying that the transaction identifier is not found in the receipt. I have confirmed that locally, in the app. Even after refreshing the receipt, sometimes the transaction identifier can't be found.
Also, the purchase has succeeded because trying to buy again the same subscription prompts an iOS pop up saying that the subscription is currently active.
Obviously this strange behaviour is happening in the sandbox environment. Also note, that I am using up to 3 test users switching back and forth between them.
Has anyone experienced a similar problem?
Any ideas about what is going on?