As playing a multiplayer game, after 5-15 minutes of playing suddenly something happens to the game and FPS drops to a very low value, something like 5-10 where before was 40+. What's interesting after the bug appears, all objects (even the most nearby) switch to the lowest LOD detalizaton. For example, all bushes begin to render by onle to polygons, as if they were far away. After the bug occured, there's no way to recover the situation, the FPS low even in main menu. The only solution is full restart of ARMA.