The Soviet-era 9K38 Igla man-portable air defense system, or MANPADS (depending on the version, launching either the SA-16 [Igla-1] missile, the SA-18 [Igla] or SA-24 [Igla-S]) is very effective. When South Africa tested the SA-16 against the then-current version of the US FIM-92 Stinger missile, back in the 1980's, they found the former to be superior to the latter.
Nevertheless, to be effective, the Igla has to be launched successfully. If you fail to achieve that, interesting things can happen - as a hapless soldier found out during the recent Clear Sky 2020 military exercises in Ukraine.
I'm not sure what happened. I know some missiles can be "locked" into their launch tube, to avoid slipping out while it's being carried: so I guess it's possible that this missile's lock had not been released. Alternatively, it may simply have stuck in the tube, either through dirt or debris being present, or through being improperly inserted.
Whatever the cause, I wouldn't be surprised if the shooter had to change his underwear afterwards!