Hi Raymund,
Just check below things :
1) Selection criteria is correct i.e. there is a corresponding position in the system for the selection criteria . Check Valuation class, portfolio etc.
2) There is Node (Updates types for Portfolio Transfer ) in IMG which has to maintained and account assignment has to be set up for that update type.
3) You have to create the Position Indicator for the position (New Portfolio) to which you are doing the transfer .
I think your error is related to point.1 but it would be good if you check other 2 points too.
Let us know your feedback.
Cheers !
Adi