My experience with LLM's is that the "fallback" issue is probably one of the most serious issues. I have seen zero talk about it outside of this thread. I'm not sure its even being worked on. The llms have this terrible drift towards always making something happen even if that thing is not even related to the task at hand. "failure" in the sense of simply throwing an error/exception is something models seem highly resistant to.

I cant tell you at this point how many times I've seen them do something like

Fail > make up values > maybe log it > keep working silently with increasingly corrupt data.