Have had a series of events and conversations recently that merged in my brain earlier today - let's see if I can reconstruct the way they seemed to go together.
1st - a recent conversation about a workshop on saying "no" - when should interpreters turn down work? It's been reconfirmed for me that one factor is clearly CONTENT. If you are not familiar with gay history, don't take a job that features someone discussing this history! Or, if you can't imagine the act of teaching, interpreting a training seminar for teachers probably isn't your thing.
It's not a question of language production or reception, if you lack the contextual knowledge it's just a real stretch to be able to produce an interpretation that makes sense. Most of us can't do it, regardless of how smooth our ASL might be.