Can't delegate 2nd signature to same person - "already party to this agreement" error

We have a requirement where a document could be signed twice by the same person (email recipient) - acting for two different roles.

The agreement is initiated via API using hybrid routing and two Recipeint Sets with sequential signing Order.

This works fine, however if the recipeint tries to delegate to another person , the second delegation sometimes fails with the error:

"You can't delegate your signature to xxxx who is already party to this agreement"

How can we allow signatories to relaibly delegate to the same person, twice?