CarlosG, make sure the side shock is not mounted upside down at the chassis brace end. If the extended part of the ball is not down towards the spacers it will slightly bind and cause just the probem you are having.
And yes it will mount up that way. All it takes is being in a slight hurry and having a 2.5 mm allen head in your hand instead of a 3 mm. Don't even ask how I know ;-)
Ed M.