I'd suggest you try taking some links out of that chain before anything else. It seems to 'droop' when it's sat in place. Fine for bikes but all the chains we have (hydras and SMIDSY's drive) have chain tensioners and guides.

A chain tensioner is either an idler sprocket which you fix onto an adjustable arm to push the chain tight or you can use a piece of HDPE/nylon 6 bolted to an angle where you can move the HDPE up and down.

The chain doesn't need to be mega tight but does need to avoid the amount of slack you can see in the video whilst it operates.

Guides on the sprocket may also help. Nothing special but you can cut a piece of 3mm ali and bolt it to the sprocket on a spacer which will help the chain 'feed' onto it.