We have set the Transferring purchases seen on multiple App User IDs option to
Keep with original App User ID. We are testing with the sandbox user.
Here is the scenario :
1. User A do the signup with device A and make the purchase so device A’s playstore account linked with User A.
2. Now At the same time if User B tries to purchase in device A it fails as expected and purchase remains with User A.
3. After 2-3 days if we try with User B, it allows and purchase get successful and device A is now linked with User B. Which in this case should not allowed.
By setting the option to Keep with original App User ID. it should not allowed this. We are testing it in sandbox and we wanted to make sure this never happens in production.
Sandbox does not reset the linked app user id. The expected behavior is that User B will not be able to make a purchase when signed in with the PlayStore account of User A.
I recommend that you create a support ticket for this and include the user ids so we can look into our logs to see what exactly is happening with these two users.