Quad Drive Speed Change

[Mini Me]

I have a quad drive Protool drill (same as the Festool but painted black), actually I have two and one went back under warranty to have the impossible to move speed change fixed and it still works but is very stiff. The second one now out of warranty has reached the same stage of being impossible to move and I wonder if anyone has a simple fix, pulled one apart themselves or do I have to send this one back as well and pay for the repairs. Thanks.