When you have a text custom field duplicated in multiple team-managed projects, it causes the JQL "custom field" is EMPTY to list all issues including the ones that have value in that custom field.
- Create a custom field with the same name in 2 different team-managed projects
- Put values in some issues and leave others empty
- Use the JQL (project = P1 and "custom field" is EMPTY)
Only the issues with the field empty should return
All issues are returned including the ones with values
Use the syntax
project = P1 and cf[id] is EMPTY