Context:

• given:
  • I create a user task report, grouped by user task, distributed by none
  • I add this report to a combined report
• when:
  • I change the distribution to assignee/user group and click save
• then:
  • the report is saved immediately
• expected:
  • I get a notification that changing the report is a destructive action and will affect the combined report

Hint:
even funnier is that if I want to remove the single report than I get a notification that this report conflicts with the combined report although it's not part of it any longer