Replying to Possible law suit: REI set DIN's incorrectly, only signed off on front DIN's

Hello community, I come with quite the slander on REI... Pre-season I had my bindings remounted for my new smaller boots and had requested my DIN's be set to 7 on my Tyroila Attack 12's. When I was grabbing my skis, I signed off that they had correctly been set to DIN's of 7, but I was only presented with the front DIN's, and didn't think to check the back ones too, as I figured they were competent to set them both to 7. Fast forward to 12 weeks ago, I tore my MCL skiing after my right ski caught an edge after landing a fat air. Big bummer on the season. Fast forward again to 3 days ago on Friday, I was finally going skiing again and wanted to lower my DIN on just my right bindings to protect that knee a little more. The front was correctly set to 7, however, the back of the bindings had a DIN set to 9! Both of them! I have not touched them since the shop originally set them this way, so I am currently outraged, I set both the back DIN's to 7. Now I am wondering what I should do, there is a high likelihood that REI's incompetence is the reason I tore my MCL or at least contributed to it. Yes, I signed off on their waiver after checking the front DIN's but not the back DIN's.

What should I do here? Try and get some under-the-table compensation? Is it worth a try? Threaten a lawsuit? Has anyone had any similar experiences?

I have attached an image of the DIN's before I set them correctly myself. It is easy to confuse the 7 and the 9 on the back binding as you can see.