For a Jira project I created a custom issue type called "Fristenüberwachung".
When I use the Create button from the main menu at the top, I can create tickets with the type Fristenüberwachung without any problems.
When I try to create a Fristenüberwachung issue within an epic, there is an error message saying that the issue could not be created (see screenshot).

If I choose any other issue type, there is no problem for creating issues from inside an epic.
If I create a Fristenüberwachung issue from outside of an epic, it works fine, and I can associate that issue with an epic afterwards.
Any idea on how to resolve that problem ?