wrote:

Is the torsion shaft hollow or solid?

On a hollow shaft it is very rare for them to slipped & the bolts don't
need to tightened all that much. The set screws will make an
indentation in the shaft so it's not likely they will slip unless
someone loosened them.

If it is a solid shaft it is possible for them to slip if there isn't a
keyway in the cone or if one of the set screws aren't set into the slot
in the shaft.

Doordoc
www.DoorsAndOpeners.com

The torsion shaft is hollow. The slippage is not on the side sleeve where
there are bolts to be tightened but on the center sleeve where the torsion
spring grips to.

This brings me to my next question. Why is the torsion spring not bolted to
the center sleeve (which is mounted on the wall) instead of having it grip
the threaded sleeve? If it is bolted then there is no chance it will slip.

TIA for any help.