Cause

Two cut-outs (rectangles, slotted holes or drill holes, etc.) were placed on a mounting surface so that they overlap either completely or partially.

Solution

1. Locate the two cut-outs in the layout space by using the Go to (graphic) and Go to 2nd coordinate functions from the popup menu of the Message management dialog.
2. Move one or bothe cut-outs on the mounting surface so that they no longer overlap, or delete one of the cut-outs.
3. Then start a new check run.