I am currently paying the Stormcloak missions and I am nearing the end. I was told to meet the Stormcloak soldiers at the gate of Fort Hraggstad to launch an attack on the Imperials inside. I got to the indicated point and there were no Stormcloaks, I went inside and there was only 1 Imperial soldier. I killed the Imperial and another 1 spawned a little while later (At one point the Imperials turned invisible for some reason o.O), I continued killing those soldiers until I was down to 5% of the Imperials left. Then the Imperial stopped spawning...

Now I can't do anything, I have one save right where the Stormcloaks were supposed to be before I entered the fort and another is too far back and the autosaves were made at that fort due to my frantic attempts of fixing the bug.

Can someone tell me how to either, Fix this bug or what cheat code I can enter to skip this mission, along with the quest ID or something? (Also I can't do the 'sqt' code since I have about a million other active quests...)

Thanks