My only 2 revolver failures ever!

S&W 629, very cheap factory reload ammo, projectile moved forward in it's case locking up the cylinder, could not rotate or open cylinder, complete failure to function, pushed pushed bullet back into case, fired round, functioned perfectly after that.

Colt Trooper MK3, when I cleaned it I used grease on where the cylinder rotates on the crane, after 50 rounds of .38 special dirty range ammo, it would not rotate in double or single action without manually rotating the cylinder, and that eventually quit working, locked up solid. Cleaned it & oiled it, worked flawlessly.

Don't use grease on rotating parts, and Dont carry re-loads, unless you trust your own re-loads.