OKAY!!! The little plate thing that goes in the groove may have oil dried up under it - take a q-tip and a little solvent and dab it a little in every direction - especially inside and under that plate. You may have to lay the machine on it's front on a towel to get it worked in - protect your paint - pack something to catch drips - see if anything happens. I don't know if rubbing alcohol would free it up a little or not. It may have dried up oil in the slot or on the bottom of that little plate thingy. Put solvent on each notch above and below, too. Get yourself a really good light, too.