Unity In-App Purchase Local Validation is slow

I'm currently changing our game's in-app purchasing model from an older add-in to unity's built-in service. Up until now there have been no issues testing payments and validating receipts, both live and using sandbox accounts.

Following the Unity guides I have developed a store, and can successfully make new payments with a sandbox account, however local validation takes around 2 minutes on an iPad Air 2. Is this normal? Our previous add-in validated receipt data using the App Store, and took only a few seconds.

 private bool CheckReceipt()
     {
 #if UNITY_EDITOR
         Debug.Log("IAP: Default for editor, receipt valid.");
         return true;
 #elif UNITY_ANDROID || UNITY_IOS
         try
         {
             CrossPlatformValidator validator = new CrossPlatformValidator(GooglePlayTangle.Data(),
             AppleTangle.Data(), Application.bundleIdentifier);
             Product product = controller.products.WithID(ProductID);
             string receipt = product.receipt;
             if (receipt == null)
             {
                 Debug.Log("IAP: No receipt.");
                 return false;
             }
             Debug.Log("IAP: Validating receipt...");    
             IPurchaseReceipt[] result = validator.Validate(receipt);
             return result[0].productID == ProductID;
         }
         catch (IAPSecurityException e)
         {
             Debug.Log("IAP: Invalid receipt, not unlocking content");
             return false;
         }
 #endif
     }