Originally Posted by
FBinNY
You should never assume.
So your problem may be because of a brand or type mismatch, or possibly misalignment which has you riding with the cleat beginning to unlatch.
I'd start by clipping the shoe to the pedal without your foot inside. If it's sloppy, you know there's a problem with the cleat. If it latches well without a foot, but not with, then maybe it's an alignment question.
I've had the spin instructors place my cleat where it needs to go, but it just never engages with the pedal. I'll try to get pictures, but it was just so disappointing to finally buy shoes after years of spinning class, only to find out they're not working.