I had that problem with my Eldredge Two Spool just yesterday. I had to tap it with my foot the make it stop sewing.
Then I realized the lever wasn't coming all the way back up when I took my foot off the pedal. But that machine is very old and has been sitting in shed of my young sewing machine guy no one knows how long. Even his father doesn't remember from whence it has come.
So I unplugged the machine, and pushed down on the lever multiple times. I could hear a sort of grind, as if there was rust or something in there. But as I worked it got better, and last night it worked just fine. I would take it apart, but there are no screws, so I'm afraid to try. I guess I'll take it back to my young sewing machine guy and have him look at it.