OP should Google this question, particularly DieselStop.com. I have read of a few cases there. However, those who have no failures don't seem to post much.
I don't believe that this is a frequent issue. It is unfortunate that Ford chose to use level sensors (like on your RV tanks) instead of a level gauge as is used by Ram. I've had one false indication in 82K miles on our 2012 F-350. The owner's manual says that it will reset the DEF management system warnings in 4 starts, and mine did. These 6.7 engines are worlds better than either the 6.0 or 6.4.