Cause

There is a branch (e.g. a T node) in front of the arrow stump of an interruption point which has the property "Star source". This means the arrow stump leads to two targets.

Solution

Possibility 1

Delete the branch (the T node) of the interruption point so that there is only one remaining link to the star source.

Possibility 2

Delete the branch (the T node) of the interruption point so that only one link is the target of the star source's arrow stump.

Refresh the connections and then start a new check run.