I have the same problem, I am new to the foundry editing, and was in the process of learning by creating a new mission, and playing around with the foundry. Since then, I have left one fleet for another, And have my old fleet name tagged in the project. While trying to delete it, It would CTD. I created a new one with the new fleet name, but was unhappy with the name. (no editing done at all). Tried to delete it, and again, a CTD. I gave it a few days, and still cannot delete it.
If you need ticket numbers for mine, let me know. Perhaps you can find familiarities between the two.