Reproduce transactions as new transaction id when repurchasing an auto-renewable subscription

I was building an app which has auto-renewable subscriptions.
When I try to resubscribe the subscription I subscribed before, then iOS shows the dialog, “You’re currently subscribed to this.”, And enqueue all of the transactions I purchased in the past into a default transaction queue. The statuses of the transactions are SKPaymentTransactionStatePurchased. As a result of this behavior, I have to process vast of transactions. This happening was in the Sandbox environment.
 
I expected to enqueue only one transaction as SKPaymentTransactionStatePurchased.
 
The following list is my scenario that reproduces all transactions:
1. Subscribe a product
2. Subscribe the product purchased again
3. The dialog, “You’re currently subscribed to this.”, is popped up
4. Tap ok button
5. Press Home button then close my app
6. Tap and launch my app again

I tried to solve this problem throughout the day. Finally, I created a new sandbox user and just used it for purchasing subscription. Then this behavior has no longer occurred. I don’t know why such things happened.