I played with Germany (hardest/aggressive) - and many events never occurred. I tried to stick to the historical events, but when Austria-Hungary was defeated, there were no ministers in Austria. It's May 1918, I took Lithuania and some other Russian provinces, but an armed insurrection in Petrograd and other events never occurred. Do you know why is that?
Also, Bulgaria went armistice without even being attacked or loosed a province.
Did you send Lenin back? I had a game where I was hammering at the gates of St Petersburg and had the Russians in a total route but had forgotten to send back Lenin.