Actually, that headline covers most of this. Kotaku summarizes a reddit thread on the maddening inconsistency of hitboxes in Counter-Strike: Global Offensive, as the shooter does not seem to always properly acknowledge bullets hitting their targets. After a GIF showing this in action gained traction, Valve's Matt Wood chimed in explaining this years-old issue will be addressed at some point, saying: "Hi, Kevin. It's being worked on. We don't have an eta."