Issue shows up both as swimlane and as Issue in overview when grouped by Parent Task

[LilMouse]

I have a task ("Subproject Issue") with a subtask ("Subtask").
The cards are grouped by "Parent Task".
But now my issue ("Subproject Issue), shows up both as a swimlane and a task in the category No Parent Tasks.

Is there a way to only have it as a swimlane?

Because I don't see the parent task showing up in the screenshot on the readme: https://github.com/jgraichen/redmine_dashboard/blob/main/docs/rdb_2-1.png

Extra info:
Redmine: 6.0.5.stable
Plugin: 2.16.0