I have a MacBook Air and I often run ScreenFlow on it. However, I find that the hard drive gradually filled up, even though the SF scratch disk is assigned to an external drive. Furthermore, its impossible to find what is clogging up the drive. If I look for invisible files I can't find any large files. The last time this happened I had to wipe the drive. Any ideas what or why SSDs clog up without the source being discovered? There is a missing 42GB, as its says there is 120GB drive but I can only add up about 78GB in file usage.