Well, I've had some great success recently with lucid dreaming (ended a dry spell with back to back lucids), but last night I would've had my 3rd night in a row with a lucid except there was a problem. My favorite reality check failed (the nose plug RC).

In the dream I was in school and the teacher handed out a paper that was about lucid dreaming and I said to myself, "there's no way this is real... why would we be learning about lucid dreaming?" so I did the nose plug reality check and I couldn't breathe through my nose. I was disappointed in the dream because I thought for sure I was dreaming.

Why do RC's fail sometimes?

To prevent this should I do multiple reality checks from now on to double check (literally)?