When I start Arma 3 Dedicated Server with compatibility data I get this warning:
17:44:30 Warning Message: No entry 'bin\config.bin/CfgAmmo/lxWS_B_SG_HE.simulation'. 17:44:30 Warning Message: '/' is not a value
The full RPT-file:
app_update 233780 validate
workshop_download_item 107410 2636962953
Verify integrity of game files. Compatibility data mod files are exactly the same as the dlc build.
Did so, as well as redownloaded compatibility data a few times and compared sizes with bought DLC -- they were the same. As a workaround I uploaded to my server bought DLC.
It's for sure a Steam issue, since I just booted up the game with only the compatibility data active and everything worked fine.
Can't say for sure -- I didn't check compatibility data with the game (since I have bought DLC), only with Arma 3 server.
Just redownloaded compatibility data, and now it works fine. Looks like the problem really was with Steam.