On earlier models of the Titan/Centaur wheel clamp the lock when in the unlocked position is retained by the red plastic cap which also stops it from spinning. Over a period of time this may become loose and will require to be pushed back firmly against the face of the lock face with your finger or thumb.

If the hood is not locked in place and the lock spins around when attempting to lock it into position then there may be an issue with the order in which the arms have been arranged on assembly or the orientation of the disc spring. Please refer to the attached instructions which detail these points.