Only partially working within inline_entity_form (mulitple)

Situation

entity type A has a select referencefield to type B.
entity type C has an inline entity reference referencefield (cardinality n) to type A.

When creating or editing type C entites ddf only works for the first inline entity (type A, ddf for referencefield to type B).

I have to admit that I did patch the js in oder to fit my needs (enabled self-referencing; fixed argument to only use the first -> see patch file attached). However, I don't think these changes are the source of my problem.

the problem

the javascript seems only to ever be attached to the first inline entity loaded.

Any hints on how this could be fixed?

tia