After a little digging I have located the issue.
I introduced this pipeline as a replacement for the webhooks to runbooks to pause and resume.
https://learn.microsoft.com/en-us/azure/synapse-analytics/sql/how-to-pause-resume-pipelines
The pause and resume activities are held within a switch condition. The activities within the switch do not react to the factory validation output. As a work around to stop this error reoccurring, I have added dynamic body content: @markus.bohland@hotmail.de ('{','}')