Revert back to DX9, check for "loading game files to RAM" option, disable mandatory in-game patching; as the last resort, run diagnostics of your hard-drive or at least do a defrag once in a while, possibly cleaning it up for more space as otherwise it drastically decreases the overall performance. The last suggestion applies to mechanical hard-drives on both the consoles as well, although you can't tackle with them, just wiping out the data you don't currently need to free up space.
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It may or may not be a bug. shut off the program if nothing on the screen is moving (blinking lights, etc.). Reload the game and try again.