In-app purchases background problem

I implemented in-app purchases in my app that is sending the receipt with the user ID (that I get from Memory) to the backend before finishing the transaction. In Sandbox and TestFlight, the in-app purchase is working fine. But the problem is that when I am in production, the user ID received at the backend is nil.
Is it possible that the in-app purchase is killing every background process, so that's why I am unable to get the user ID from the memory?
And do you have any idea how I can solve this issue?
Thanks!
In-app purchases background problem
 
 
Q