Be sure to either spray or grease the sides of your cake pan well. When done baking, let sit in the pan for about 10 minutes and run a knife around the edges and then flip over onto a cooling grid. It looks as though you are not loosening it from the sides or you could be tuning out too quickly. HTH
It looks like you may be using too much grease and flour so that it is breaking down the outer edges of your cake mix. I put parchment paper in the bottom of my pans and spray all with cooking spray (Pam). Let sit for 10-15 minutes after baking, then loosen sides with a knife, a plastic one to avoid scratching the pans. Also, check your instructions for oven temperature. I haven't used a boxed mixed for a long time, but they used to recommend 350. With the strips and the lower temperature, maybe the sides aren't getting enough heat to form a stable edge. Good luck!
Rather than separately greasing & flouring, I find that pan grease works much better at not drying out the sides of the layers.
I use the Wilton type in a squeeze bottle, but you can make your own:
Equal parts all-purpose flour, shortening, and vegetable oil, mixed with a hand mixer and stored at room temp. in a covered container. It lasts for a long time.
I also bake at 325F and don't use baking strips.
I have a couple cake recipes that do that. I have found if I use parchment around the entire pan, I NEVER have anything stick or crumble! I put a circle of parchment on the bottom of the pan and then line the sides with strips of parchment. It works great and you can turn your cakes out of the pans as soon as they come out of the oven. My cakes are never dry from the cakes continuing to bake in the hot pans when they come out! :)
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