I do, yes, always bahtinov-mask. This is a problem due to flexing in the thin metal around the focuser I think. It is evident when I look at the stars through the OA guider: when the scope is pointing one direction the stars are fine, pointed another direction they are elongated. It's a real pain in the b**t and I just ordered a pair of Parallax rings to try to fix the focuser. The plan is to drill holes in the rings and bolt them to the focuser. I'm hoping it will work, otherwise I'll have to look for a different scope.
Best regards,
Ginge