Prolly got something figgered out by now, but if it was a Turbo Conveyor, I would say that you dropped a spacer and it got pinched. A Jorgensen is likely the same problem, but I've never had that issue with a Jorgensen.
Just gotta force it. Most likely backwards.
On my Turbo's (POS's) when they start to git stuck like that, I run backwards for some time, and then you can hear a spacer(s) jingle around up in the head end, stuck inside. I drill a 3/8" hole, then a 3/4" EMT knock-out, and then you can see up in there, and reach in with a magnet/stick to fetch the offenders out.
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Ox