I’ve stripped and re-built a couple of these (my wife says I have a problem, as I keep buying them when I see them going for a good price… 😂), and that sounds to me like it might be a tension problem on the quick release?
Are you sure you have the spring tight enough? When I rebuilt my last one I had a similar sound and the quick release handle was very soft. I wound the spring up a bit more and it all went away.
Also, while you can pack the end cap with a washer I have not found it to make any material difference to the operation of the vice, just cosmetic.