As you may very well know from others, L4D2 has been having some checklist problems ever since The Passing DLC came out many months ago. The achievement for Port Of Scavenge won't stay checked and there is another that has an incorrect point value, giving the game a total of 1260.
As I stated, you likely already know about this but it doesn't seem as if anything has been done to rectify it so this is just a friendly reminder. If there has been a message somewhere stating how to repair this then I apologize in advance. If that is in fact the case, please message me a link to such article. Thanks.