Response code 100 when post object has more than 3 relations

[thejimu]

I wanted users sending a POST to be able to include new relations within the POST so I extended using onAfterDeserialize which then creates the relations and replaces these items in $payload with their IDs. It works fine and returns 200, except when there are more than 3 relations in which case it still creates all the objects successfully but returns response code 100, and I am a little bit stumped as to why.

Any advice would be much appreciated.