Anyone revolution owners out there have this happen. I remove this a number of times through out the heating season for cleaning. I have never had a problem until now. It seems loose enough but refuses to drop down out of the slots.
If it's like the one in my SCF-050, there's not much that can go wrong there. You've got to lift up the rear part so that it can slide toward you and drop out of the slots. But I'm sure you knew that. I wonder if there's some build-up on the tabs so they don't easily slide out of the slots. If so, I would think a little wiggling would loosen things. Good luck - Dave