PO delegation rules are not working as expected

Hello,

I have created below delegation rules in BPM worklist > Preferences > Other's rules > Vacation Period (using delegate to), as per the below table:

User Name	Participant	Type	Delegate To
markus.breuss@drei.com	ControllerBUC	Serial	eric.serraparadis@external.drei.com
erich.raschun@drei.com	BANF	Parallel First Responder Wins	eric.serraparadis@external.drei.com
markus.sagmeister@drei.com	LEGAL	Parallel First Responder Wins	eric.serraparadis@external.drei.com
agostino.ruberto@external.drei.com	Serial Postapproval	Serial	eric.serraparadis@external.drei.com
bernd.loacker@drei.com	Serial Postapproval	Serial	eric.serraparadis@external.drei.com
Bianca.Pfaller@drei.com	Serial Postapproval	Serial