First thing I would do, before condemning the scope, is remove the .63
Reducer/Corrector, and the Robofocus Unit, then try collimating again.
I would assume a Robo-focus, or other Crayford Focuser attached to the
rear cell would eliminate any possibility of the influence of mirror
shift, but for the heck of it, nect time you're out with the scope, try
what I suggest, and see if you notice any differences.

I've personally never heard of anyone ever using a reducer while
Collimating an SCT.

If your Diagonal is known to be good, Collimating with this in place
shouldn't be a problem, but some will Collimate without any optional
item attached to the rear cell, other than a 1-1/4" Visual Back.

Best Collimation will always be achieved at the highest magnifications
(seeing permitting) Mark