Oh HELL yes it happened to me and yes, I pissed my pants. When we first changed from the M-2 to the M-224 60mm mortars our armorers decided that they wanted to shoot a 60, so they grabbed a new-in-box gun and set it up. Dumbasses didn't clean it first, so the barrel was full of cosmoline. As I said elsewhere, we used WP rounds (with an effective kill radius of 100 meters) to set the base plates, so they dropped a WP round to set the plate. It made a weird sucking sound and dropped about 15 meters in front of the gun, which was also about 40 meters from me and 45 from where the ammo was stacked. Of course it didn't go far enough to arm, so it didn't go off, but how much do you trust the lowest bidder? It looked remarkably like the example in the video.
More to @atomheartbevo's point, I saw quite a few 60mm mortar rounds and LAAW rounds that fell less than halfway to their targets due to malfunctions in the propellant charges. Thank God for functioning safeties.