Either you bought and aftermarket one or it is defective. They work by friction. 2 outside pieces of metal sandwich the lever so it will stay in place. If it was not tight enough then it will slip back. Some times a simple squeeze of the 2 outside pieces will work to fix it. Some times you drill out the pop rivets and replace with nut and bolt. Or you call up who you purchased it from and make them give you one that works.