Another tilt question - 61EDPH

[OK Apricot]

Hi guys, 

Been becoming more conscious of eyesore stars in one half of my images. As I look at the sub frames, the left side corners have lovely round points for stars, but the right are elongated, and along the same plane at that. They don't really show a "fanning out" pattern from centre like you'd expect if your sensor was too close to the reducer, but the elongation is the same plane, size, direction etc in both corners. 

My reducer has a rotator so I've nipped up the tensioning bolts so that it's tight to eliminate that, I've tightened the OAG thumb screws one at a time half a turn at a time to get the most uniform "grip" so that the bracket is square in the optical train. The focuser rotator looks and feels well built and I can't see or feel anything from there. 

Tested tonight and it's an improvement over my last outing, but I'm still not satisfied. Packing away earlier I put the scope in its usual position in the lounge and with both lights on I could see and feel "slop" in the focuser draw tube. There is a little silver grub screw on the part of the focuser that the tube slides in and out of, but it's on its own and opposite to the focuser rotator lock knob.

What might be the best way to take up the slack in this scope's focuser with this arrangement of screws? 

Many thanks in advance 👍