Same exact thing happened to me at the same exact place. I was going up the stairs to the third floor of the fire station tower. When I reached it I walked towards the middle of the room to check out some loot and "crack", I now had a broken leg for no apparent reason. I did not go through the wall, I was not lagging, I did not get shot (no one else was on) and I did not make any sudden movements. Just normal walking. Hopefully this information helps the devs address this issue.