I use a hammer and tap each side of the stand into the slot until it will not go down any further. The only problem is that it take's me a half hour to take it off.

Only kidding on the hammer. I force it down as deep as it will go with my thumbs and every once in a while give it some more thumbs down treatment. It seems to work as long as do not put any music on it.
Only kidding again.
I have charts on cardboard for each song. No heavy books which elimates the problem.