Couldn't find this in the forums, so I decided to write about it.
Although it's just a minor 'problem' (doesn't affect the game anyway) I found the completion percentage is sometimes a little confused, when you do the following:
1) Open up the achievement menu while playing on a server.
2) Press Escape and return to your game
3) Press Escape again - now the completion percentage may have changed
-> This does not happen if you close the achievement menu and reopen it the next time. Furthermore if I see the menu showing 96 percent, close and reopen it, it shows 95 again.
I do not know WHY this happens, can it be because I'm near the completion of another achievement? (6 timed mines kills to go)
Another thing I found: sometimes you can hit the wall BEHIND you with your knife.
Check out the following:
1. On Control make your way to the top level and position yourself to the right of the big screen, so your back faces the wall and you can see the ladder leading down across the room.
2. On Temple position yourself in the big room in the corner on the pathway above the body armor, so you're looking down the ramp.
But I guess that's some problem of the source engine itself.
EDIT: Here are some screens from facility. Seems it occurs mostly when you're ducked against the wall. (@screen 2: I did hit the floor once by accident, that's why there is the red spot near the radar)
