Прислали ответ после присланных файлов из поддержки:
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Hello,
please try clean reinstallation of Arma 3:
1. Uninstall the game.
2. Make a backup of Arma 3 folder in Documents.
3. Delete both Arma 3 folders in Documents and Steam:
\Users\*YOUR USERNAME*\Documents\Arma 3
\Program Files (x86)\Steam\SteamApps\common\Arma 3
4. Reboot your PC.
5. Run Steam as Admin, download the game.
6. Try to run Arma 3 (without mods).
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Попробую - отпишусь.
