I know this is like a Pandora's box, But I just can't get my head around why expired subscriptions would still generate issues even after the expiry date.

To replicate :
Create a subscription that would end in the past
1. Search for a record in the staff interface
2. Click on the title to go to the record details page
3. Click on New > New subscription
4. Click Next
5. Fill in the second part of the new subscription form
   - First issue publication date : enter a date in the past, e.g. 2020-01-01
   - Frequency : choose a frequency, e.g. 1/3month
   - Subscription length : enter a number of issues for the subscription, e.g. 4
   - Subscription start date : enter a date on or before your first issue publication date, e.g. 2020-01-01
   - Numbering pattern : choose a numbering pattern, e.g. Number
   - Begins with : enter a number, e.g. 42
6. Click on Test prediction pattern
7. Click Save subscription

Receive one issue for this subscription
8. Click Receive
9. Change the status to Arrived
10. Change the Expected on date to something close(r) to the Published on date, e.g. 2020-01-01
11. Click Save

Make one issue late
12. Click Generate next

Receive the rest of the issues normally
13. Repeat steps 8-11 for all remaining issues

-- Once you have received all issues in the subscription, it should say "Subscription expired" in the Serial collection page.
-- Note that the next issue was automatically generated even though it's not supposed to be in the subscription

Like Katrin said in the chat, I don't think receiving should be completely forbidden in expired subscriptions as there can be late issues that you might receive in the future. And the act of "receiving" is actually editing the issues, so if I need to mark one as "Missing" in the future, I need to be able to do that even when the subscription is expired.

But, I don't think additional issues should be generated after the prescribed number of issues/weeks/months in the subscription or after the subscription end date. My problem is rally with the automatic creation of issues.

Although I must say, I don't work in a library, so maybe what I'm saying doesn't make sense in a day-to-day serial workflow. But I did receive a question from a client asking why issues were still being generated even after the subscription is expired and I can't find a logical explanation.