The Remington built Marlins leave a lot to be desired. If it is the spring loaded catch in lever that is sticking, you can often change out the spring in them for a lighter one to improve operation. A dot of grease on it helps too. Otherwise the internals can be quite rough and crude. It's simple enough to remove lever and bolt and do some polishing. Put a bit of lube on the knob on end of lever were it enters bolt. Time and use may smooth things up a bit. Sad that Remington who once made such fine guns deteriorated to the pathetic state it was at the last.