Cannot recall any significant stability issues when last I played a four-person scenario using the version 1.08Q patch. That said, I seldom attempt to run more than about two-turns without saving, exiting and re-starting the game. Although the AI might produce odd results as it functions as both your ally and enemy you can tweak it somewhat. Examine the country files found in the ...\World War One Gold\Data\AI\Modding folder ensuring that you save the stock files before editing. Beware for unintended consequences though and good luck.