This exact error happened to me earlier today. Are you, by chance, subscribed to the "Tidy Up Meister" or "Alternative Inventory Rendering" mods? Both mods updated last night / this morning so I wonder if one of them is causing this sound file mismatch error.
My local version had a few sound files (including deserteagletxt) that reflected today as the Date Modified, whereas the server still had files from February. I "fixed" it by uploading any newer sound files from my local game version (C:\Program Files (x86)\Steam\steamapps\common\ProjectZomboid\media\scripts\weapons) onto my dedicated Multiplayer server (home/media/scripts/weapons). I use GTX Gaming as my host so the file path may differ. Make sure you back up your server's sound files just in case.
I put "fixed" in quotations because the true test will be whether others can join the server. I have 3 buddies who are going to hop on tonight. If they get the error, then my idea of replacing the sound files will have failed.