My old F & R Cub 3 jas a jammed feed dog lever - how can I unjam the lever?

Hi,

I am giving my mother's Cub 3 to my daughter on which to learn sewing machine basics. The lever to lower/raise the feed dogs is jammed and won't move. Any suggestions how to unjam please? I have followed instructions for ALL the oiling points (which involved removing most of the casing) but the lever doesn't seem to have any accessible oiling point. The machine does produce quite a decent stitch for its age.
I am also giving my Cub 7 (37 years old!) to my elder daughter as I have at last bought a new machine - a Necchi Sofia 300. Yippee! Sad to leave the Frister and Rossmans though. No probs with the Cub 7.