TL;DR - After cinching down the cover for the tent a few hundred times, the stitching for one of the buckles on one of the cover straps ripped out. I sewed it back together and everything is good again.
I think there was probably some very minor manufacturing defect in one of my straps that only reared its head after I used the strap a couple hundred times, since I inspected the other strap and it looks just fine. This is one of those things that some might feel like they needed to buy a new strap for, but fixing it is so easy - just a needle and thread - that I totally recommend doing this kind of thing yourself.
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