There's multiple times following error... e.g. when player chooses an axe and starts hitting zombie with it one of the following happens:
- it actually is an axe
- one does not have an axe but in fact
2.1 just bare hands
2.2 firearm.
Common to 2.1 and 2.2 is:
-Player sees the supposed object and doesn't know that it's in fact either object 2.1 or 2.2.
-Team mate sees the actual object (2.1 or 2.2).
Common to 2.2 is that player doesn't also hear the shots but team mates will.
There's no specific conditions when this happens. It just happens randomly whenever.