Believe it or not, that is not the most unusual failure that I have seen on a FAT.
We had a downtube split open on one bike. Apparently, True Temper had a welding issue with one lot of the seamed tube used to make our downtubes. This one manifested itself shortly after the customer took delivery and put in some hard miles on it.
The longitudinal seam weld fractured and propagated along the entire length of the downtube. It looked like somebody took a can opener to the downtube and split it open from the head tube all the way to the bottom bracket. The welds joining the headtube and bottom bracket held up so the frame did not fold up and the rider was not hurt in any way. We were amazed when the frame came back to our shop. Wish I had a photo of it. We immediately replaced the frame under warranty and located all of the downtubes in our stock that had the same lot number and returned them to TT. They did an RCA and stated that only that one lot of tubing was affected.
That was the one and only instance that I ever saw. Hopefully no others had the same fate after I moved on.
Scott