One of the legs didn’t get pulled back all the way in the fill stage (or moved). And that corner joint looks like it’s about to come out due to that at most maybe 1/2” higher post.
That corner joint is a big concern. I would drain at least 3/4 of the pool to see if you can move the leg and get the rail back in. If you can move it with 3/4 of the water out then take more out until you can move it.
NOW the big question...............what is under the legs to keep them from sinking down into the dirt?
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