On Saturday, July 31, a group of ten cavers were doing a through trip of Bone-Norman Cave in West Virginia. At a constriction called "The Devil's Pinch" they had doubts that two of the group, Harry Fair and George O'Neil, would be able to make it. Three went through but when Fair tried, as speculated, he could not make it, though he tried, failing several orientations. O'Neil then tried, failing several times but continuing to strip down until he was shirtless, greased with vaseline, and sliding on plastic laid down in the constriction. With one companion pulling and another pushing, he made it through. Fair had to retrace the route in, by himself.
NSS News, December 1994 (Part 2) V52N12, Page 395.
Chuck Frostick "Bone Norman" The West Virginia Caver 11:6 Dec, 1993 p 17.
I guess nothing can stop a determined caver. However, what would have happened if the individual would have got stuck in "The pinch"? Also, it is unsafe to solo cave as the one individual had to do since he could not get through the pinch.