Lost various citadels because of a sudden desconexion

This happends various several times!! I was preparing the zone around citadels reaching towers to try to get better things on citadels and when i try to do them, there was a suddenly disconexion and when i enter the game again It sais that the mapp was failed!!! This piss me off so much because of time that i spent on this and for nothing. I dont know what you need to do to fix this kind of Bugs, but please. This happens already several times.
Sorry if my english is not correct.