ive even seen the calls that say they wont lock up with spit still do it. as said above upside down reed, foreign materials or u may just spit alot. when reeds get worn out too they tend to do it more often as well. couple tricks ive learned is i put rainex on all my reeds that helps a lot. also if you have a double drop lanyard u might be able to adjust the way the call hangs so the spit will run out the back with gravity. i know some contest callers that in between routines take a dollar bill and stick between the reeds to dry it out. also blowing into the back of the call will free the call up as well. hope these helps.