There were a documented number of tanks that had issues with "swelling" tanks. Funnily enough, in 2011 the fuel tank got a revision (part #62921-07 went to 62921-07A). Coincidence? who knows. I'm about 99% sure I had one on my 2012 F. H-D pretty much said "too bad for you" despite multiple sources of evidence and my bike being bone stock (at least regarding the fuel system).
The dealer was sympathetic, but I got shot down by the regional rep, who threw shade on my belt tension as being the cause-- despite it measuring properly in spec with the H-D tool and with the drivetrain properly aligned.
The Catch-22 for me was that H-D *might* warranty the claim IF they did the tear-down. But if they didn't, then I'd be on the hook for all of the labor charges.
I finally gave up, got a new tank and did the install myself.
They'e not great, but if you look at this post, you can see where the bottom of the tank was bowing out. The replacement tank was as straight as a ruler.
Just so you know-- maybe it helps, maybe it doesn't.