To reproduce:
1. Open attached project
2. Set up two Auto-renewable subscriptions monthly and yearly in iTunes connect (you can find the item IDs in SubscriptionTest.cs script)
3. Build for iOS
4. Deploy the Xcode project to an iOS device
5. Make sure that 1month option is selected in the dropdown
6. Press the Buy button
7. After the successful purchase select 1year in the dropdown
8. Press the Update button

Expected result: the purchase is successful without any issues
Actual result: the prompt on an iOS device shows a successful purchase but getting Unknown error in Xcode console

Reproduced on:
2017.4.25f1 2018.3.13f1 2019.2.0a11

Package version:
-2.0.6
-2.0.3
-1.22.0
-1.20.1

Device reproduced on:
iPhone 8 Plus iOS 12.0

Notes:
-On 2.0.0 version getting build errors, unable to build the project.
-Getting crash errors in Xcode console on the 2.0.1 version.