Well, if it's really bugged and there is no way you can complete it, you can use the console to advance the quest.
The thing is you need to know the quest ID, and the wiki doesn't have the ID for this one. However I think that it can be possible to find it.
Type in the console "ShowQuestTargets" without quotes. Now, you possibly have a lot of quests in your journal, so use PAGE UP/PAGE DOWN to scroll in the console and search for something that says Current quest and a quest that starts with "CW" When you find it, type in the console "sqt questID" without quotes, and write here what it says. We'll see where we go from here.
So i cant find CW or sungard but i guess the list would appear in the order of the quests you have right? If so then this quest is called under
current quest "freeformwhiterunquest04" idk what whiterun has to do with this quest it also says
Target 1: reference: (ff0015c9), load door: (0001a6fb)
Idk if this is the right one at all tho
Btw: the name of the quest is battle for fort sungard, its part of liberation of skyrim i hope this is enoughfor you to help me