Internal server error 500 when creating a complex business object using REST call

Summary

Internal server error 500 when creating a complex business object using REST call.

Content

Goal
We would like to store a page variable, whose type is based on the POST request of the REST endpoint of one of our business objects, in our businessobjects. The business object is a complex type referencing another business object, that in its turn references two other business objects. See attached Image.

Approach
We've recreated our approach in an example application which produces similar behaviour:

1. We defined a request and response type based on a 'complex' business object. In the example app this is the "Driver" object.