The Hobie 17 has inboard bolts and outboard castings that fit inside the ends of the cross bars where the meet the hull (at the little hump). Those casting are likely loose. They have two small "fingers" pokeing into the glass structure of the "humps". This is the vertical shear strength of the connection. They are held against the humps by small screws and possibly by sikaflex or 5200.

Dis-assemble the boat and remove the hulls / crossbars. Reseat the castings onto the hulls. You may have to fill the small "finger" holes behind the castings with resin and chopped glass. Re seat the castings with epoxy or 5200 and screws.

Be aware... the position of the castings is critical for a tight boat / ability to re-assemble. Position the castings carefully. Pre-fit with crossbars and check proper positions.