I've played around with it some more. It seems the Stanley Model 1 and the Sindoh 3DWOX have a little bit of a design problem.
They use a cartridge with a pair of feed rollers that feeds filament from the spool through a long tube to go to the extruder drive wheels in the printer. They have a clutch in the drive gearing to engage the feed rollers. What I have found is the rollers are extremely stiff to turn. The clutch is only engaged to start feeding filament to the extruder drive, then the clutch disengages, and the extruder drive wheels have to pull the filament against the drag of the spool, rollers and tube in the cartridge. I'm guessing the rollers have swelled, got gummy, or just need some lube on their shafts. Anyway, sometimes it feeds OK, but 3 out of 4 times the filament drags too much and the drive wheels gouge the filament and it jams. I have pulled the spool out of the cartridge and fed it straight to the extruder drive, and the machine worked perfectly.
I did tear the entire extruder driive apart, and found the drive wheels neede their bearings lubed. I may try to get the cartridge rollers to operate with less drag. But, plan B is to cut a hole in the front of the cartridge and make the initial feed from the spool by hand, and then let the drive pull straight from the spool, eliminating the rollers and long tube in the cart.
Jon