Platform bracket mount issues

One of my mounts for the swim platform on my 12 mojo has become loose. I pulled the platform at the lake and was able to tighten 1. I couldn't get to 1 of the other 2 since I didn't have the right size torque to loosen the studs that snug up the platform. The other one wouldn't tighten.

I thought I saw a post on here recently of this issue but couldn't find it. When I got back to my dock it was loose again. Are they just screwed to hull or is there a plate on the back side they screw into? Looking to see my options on fixing. Thanks


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