DayZ Server silently ignores mods when the mod's *.bikey file is missing or does not match the signatures (*.bisign files) of the mod's PBO files. The server listing in the server browser still claims that the mod is required, but clients that try to connect get a "Client has a mod which is not on the server" error because the server didn't actually load the mod.

Please make DayZ server report a helpful error message in the DayZServer_x64_*.RPT file when a mod cannot be loaded because the *.bikey file is missing or does not match the mod's file signatures.

Perhaps the server should also fail to start when this happens?