Symptoms

Deployment cannot be performed due to missing references
 

Diagnoses

References can be the cause of many issues regarding PandampD.
It can be Service instance, SMO GUID, Process Linked SMOs and many more.
Removing everything where possible will result in a successful Deployment.
 

Resolution

The client resolved the issue and here is what he said.
"I have reviewed the XML file of the affected workflows to verify which dependencies / references are existing. I have established that there are configured references for SmartObjects which are broken. Therefore I have removed the affected references, because from my point of view they will no longer be used."