There is not any across the board restriction that prevents users from deleting their questions within Groups. I would recommend opening a support case in your private support Group, so that a Support resource can evaluate the situation further and see if you are running into a permissions issue. The following pieces of information would be helpful to add to the case:
- The usernames of a few users that are experiencing the issue.
- The usernames of any users that are able to delete Questions from Groups, if applicable.
- Links to a few Groups or specific Questions where users are experiencing the issue.
- A description or image of any error message that is encountered when trying to delete the Question, if applicable.
- A link to one of the Spaces where users can delete Questions.