Are all necessary spacers installed and the lock ring properly torqued? The cassette must overhang the freehub (not freewheel) body enough that the lock ring bottoms on the small cog NOT the body, and be sufficiently torqued. IIRC an 11-speed body needs a 1mm spacer behind the cassette for a 10 (9,8)-speed cassette to be clamped correctly.

I am not sure what a "free wheel log nut and wrench" is but you need the correct lock ring tool and preferably a torque wrench. The typical 40 N-m torque is more than most people realize.