In prison building at northeast airfield there were some bandits under the stairs inside on the ground floor. Friend of me walked upstairs and there was no problem. I ran upstairs which caused me to glitch through the stairs and the bandits on ground floor shot me in legs+body (pants,assault vest and jacket was ruined). Needless to say I was unconcious.

Seems this only happen when you run upstairs, by walking you dont glitch through. For me I didnt saw myself glitching, Friend of me saw me glitch.