IMO this is a poor design for an aluminum frame end. The edge of the milled pocket where the hanger attaches is a stress riser and a likely place for failure. But it appears that the crack lines up differently than I would have predicted.
Warranty or no, I'd carefully sand off a bit of paint at one end of the crack and confirm it's int that it's into the metal, though the way it seems to wrap around the area, I'm close to 100% sure it is.
I wouldn't sand the entire length yet lest it give someone an excuse to deny a legitimate warranty claim. If there is a crack, I'd say you have a solid warranty claim based on the limited view of the frames condition.
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