Having a total nightmare!

No matter what I try with the tensioner the chain is jumping. Tried shortening chain and it would be too short.

Tried the tensioner lifting from below today. Same problem.

Spent hours today on this, beginning to think I may need to try something completely different.

It's a shame as I received the Grantham email I citation today too

Anyway no time to write more. Back to the Robot Shed for me