Storage incorrectly full
I have have an old 16GB iPad3 (MC705C/A) with iOS 9.3.5. It says its capacity is 12.5GB (which is guess means iOS uses 3.5GB?) and I currently have 0 bytes free. When checking the usage in settings, or when checking the storage graphs on iTunes after physically connecting to my MacBook, I have about 2GB used in apps, 1GB used vids & pics etc and 1GB in other = 4GB used by my calculations. So where is the other 8.5GB? Clearing the cache and rebooting doesn't help either. If I delete an app like Facebook which has 0.5GB it will give me about only 1MB free for about 2 minutes, then it goes back to 0 bytes. I tried this 'trick' where you try to download a movie from iTunes, even though you don't have enough space, and it forces the iOS to clear some junk, but it didn't work. I tried this 'battery doctor' app that has a secret feature to free up data, but I couldn't get the secret feature to appear. Anyone have any explanations or this, or ideas to help, or know of any apps to fix this? You shouldn't have to delete and reinstall everything to try to get that hidden 8.5GB back.
iPad Wi-Fi, iOS 9.3.5, Storage issue