Error: APT_CombinedOperatorController Null value on the accessor interfacing to field
I had the mentioned error combined with a previous warning "When checking operator: When binding input interface field" "conversion with a nullable result". All the post on the internet lead to nothing. It turned out that I had a peek and changed nullability of several attributes in this and predecessor stages however apparently DS did not really do a good job. It displayed all nullable but not all were taken as such. The solution was to delete the peek and create it again...