So, I just ran into the "other" problem yesterday. In my case, it was on a 128GB iPad where the "other" had ballooned to almost 70GB for no apparent reason. Well, after some research, the reason turned out to be that I had unplugged it during a sync and the temporary files iTunes writes to the iPad simply remained there even though the content wasn't there.
To fix, I just made sure I had an iCloud backup of everything, then reset my iPad from settings and restored from iCloud, not the computer. Fixed it right up and everything is back to normal.
Hope that helps. I'm writing in a hurry and hope I got the right details in there. Good luck!