IDOC partners and Transactional RFC partners

We've setup a system that creates an IDOC when a purchase order is created. Than that IDOC should be send immediately to the SAP Business connector.

Problem is that although when we look at the IDOC partners via WE02 we see that the receiver and sender partners are Logical Systems (the way we want it) but when we check in the Transactional RFC overview (SM58) there are errors.

For some reason other partners are used for the RFC

(in our case that was the purchase organisation and the vendor). Does anyone know what could be the origin of the problem?