Update of global assignment PrimaryFlag from update of PrimaryAssignmentFlag not working from REST?

Summary:

In my organisation we need to end assignments automatically by calling the REST API. We are using the "endAssignment" action.

We are having trouble making the endAssignment functionality work in cases where the assignment we are ending has another assignment as an immediate successor assignment within the same period of service. The constraints on 'primaryFlag' and 'primaryAssignmentFlag' seem to prevent us from making this work, since the automatic update of the 'PrimaryFlag' from the 'PrimaryAssignmentFlag' seems not to happen.

Content (required):

A short description of the starting state and what we are trying to achieve:

1) The worker has two assignments, we can call them A and B.