Gland Nut Popoff theory
Ok -- Have you ever seen a model rc airplane prop strike a hard object like the ground on a bad approach landing ? or a rock , or I guess non compressible water?
The idea is similar to a concrete post that gets an impact from a car in an accident at the bottom. The top of the post splinters from the force of the accident below but the post is ok down there at point of contact. The force magnified by a kind of standing wave thru the post appiles pressure to the top circumfrence of the post and throws any nut off and causes splintering..
Ie the model airplane hub nut is thrown off by the imapct force magified by bounding thru the shaft. Once the nut flies off the prop follows it quickly , ask an RC model flyer ,
yes the prop and shaft are ruined bent and possibley broken lying in front of the plane ...
just my theory from observations .....