The LAN missions are very buggy and are for the previous 188.8.131.52 version of DayZ.
I am working on a 1.7.3 LAN / Internet version of the SP maps we release, so you and your friends can play on them and have the same and possibly better experience as SP.
They have the same features like AI Bandits roaming the land, random AI Survivors who join up and who you can command to help buff up your side if you and your friends are working together against the Bandits and Zeds, etc. It's to promote a more ideal CO-OP experience than regular DayZ has.
The only difference between LAN and SP is...
-Can't spawn random vehicles due to anti-cheating measures (they explode if you get in them!)
However, LAN has some cool features SP will never have like...
-Custom skins on log in
-Day / Night cycles
-Persistent world game play if you have a dedicated server, so when you and your friends log off you don't loose all your gear and will spawn right where you left off