Cause
Possibility 1
The source and/or the target at the piping definition point of the piping connection in the P&I diagram have been exchanged.
Possibility 2
The source or the target of the piping connection in the P&I diagram is not assigned to a pre-planning object. The piping connection does not lead anywhere at the source or target end.
Possibility 3
The source or target of the piping connection disposes of a link to a pre-planning object, but it does not belong to the segment that was defined in the piping planning object.
Solution
Regarding option 1
Call up the property dialog of the piping definition and check whether the Exchange source and target check box is activated in the properties. If so, deactivate it.
Regarding options 2 and 3
If a source or target segment is defined for the piping object, then a pre-planning object that matches this segment has to be assigned to the source or the target in the P&I diagram. Therefore assign a matching pre-planning object to the source or the target.