Reply by PurpLev

a few questions:

1. is this something that just started recently?
2. with the tailstock lever loosened – can you lift the tailstock slightly above the bed? how far high? (too much and it means that there is too much slack)
3. do you have the clamp installed on your tailstock bold above the bolt (under the bed) or is it just the nut that keeps the tailstock ‘locked in place’? (you should have the clamp as well)
4. is there debris between the tailstock and the bed keeping it from making full metal-to-metal contact all across the tailstock (adds vibration to tailstock that can loosen it’s clamp)?

if non of the above, can you post a picture of the tailstock?

-- ㊍ When in doubt - There is no doubt - Go the safer route.