The tilt/swing lock screw provided conflicts with the A900 prism housing in the up tilt position.

The screw is too small to tighten easily with the fingers for a positive lock and is partially behind the lens flange so is very difficult to use.

I just removed mine and use the tilt adjustment without locking it. There is a tension adjustment (a "ways" adjustment in machinist terms) using a hex set screw next to the lock screw hole
and the resistance of turning can be adjusted and to account for dovetail wear.

The way mine came there is a silky damped feel to it so I don't even use the lock screw.

I am working on a modification to the lock screw which will make it work better with the A900 and
make it easier to lock the swing/tilt dovetail tightly.