I've experienced it once. In a fermenter that sat. uncleaned, on the back porch, in the sun, for four months.
It really does smell bad.
Remember one unassailable statistic, as explained by the late, great George Carlin: "Just think of how stupid the average person is, and then realize half of them are even stupider!"
"I would like to die on Mars, just not on impact." Elon Musk