It probably needs replacement. I'd turn the sprocket until it binds to try to see what is causing it. Like I said; mine had plates migrating and they ended up riding up the teeth like yours does in the video. Or, if the pins and bushings don't move freely, the chain may be stiff and could pretty much act the same. Other possibilities are bad bearings in the jackshaft allowing it to walk around (I had to replace mine) or other misalignment. The chain is the most likely, but you might as well inspect it to be sure.
If you replace the chain, you'll want a chain breaker though it is possible to get by with a vice, hammer, and small punch. This is just to get the new chain to length. The chain will come off easy enough; there should be enough slack that you can even misalign it on the sprocket and turn it to pop it off.
