Juki DDL-8700 "555 knee lift" Questions

555 knee lifter is not lifting the foot. How can I fix it? The knee lifter first started to tighten up. Now it is almost impossible to use it. I have to push it so hard, it is painful. It lifts up the

...555-5 with cpu Juki MC210 and the machine work prefectly but CPU box is not working just type 0 on memory,How do I should fix it? I put a picture for more understanding. Start out by making sure all ...