One of the most unusual stories I heard when I was working on the documentary "Made and Bottled in Kentucky (1991-92) was told by a man who identified himself as the last master distiller at Old Crow and who was by then a Beam employee working at Forks of Elkorn (formerly Old Grand-Dad and now Beam's Frankfort maturation and bottling facility), which is where Beam stuck all of the National production people it retained.
They had permission to show me around Old Taylor and Old Crow, then in ruins but still owned by Jim Beam as a result of the 1987 acquisition of National Distillers. It was just me and a couple of these old National guys. I wasn't shooting, just researching. There was no one with us from Beam PR.
This gentleman told me that in the 1960s, National enlarged the Old Crow plant and accidentally altered the percentage of setback they were using to condition their mash. He said this completely screwed up the flavor of the whiskey. Everyone, including he and the distillery tasting panel, told management it tasted wrong, but at that point they were making it as fast as they could and selling all they could make, so nothing was ever done to fix it.
A few years later, when the bottom fell out of the bourbon business, it was worse for Crow than any other major brand; double-digit share and sales losses every year. He said they finally figured out what the problem was and fixed it a couple of years before Beam bought the place, so for the last few years of production the whiskey from that plant was good.
I've never found another source who could either confirm or dispute that story.