Weird, I was having saving issues with Fallout 4 this past week. Telling me that I needed 11.33 mb to able to save my games. Checked hd - 30 gb left. Read reddit, gamefaqs, and bethesda forums. Reinstalled my game, deleted some saves = save error. Some suggested to rebuild database and I did earlier this morning and there doesn't seem to be any issues as of now.
I'm baffled tbqh. Stock hdd. It's a annoying bug that will probably show up later down the road :/
Edit: to clarify, I have encountered the issues the older posts have described too. Mainly when trying to install BF4 dlc when I have more than enough space for them.