It's this stupid error right here.
"Storage Almost Full."
It bothers me so much because I know it isn't true. I have plenty of storage space left on my iPad. But for whatever reason, my iPad thinks otherwise.
If you check out the Apple Community Forums, or even visit a Genius Bar in an Apple store, you'll learn two things. One, no one has a clue why this keeps happening. Two, the "solution" is a very annoying complete Reset. And no one wants to do all that nonsense.
Fortunately, there is a better way. It won't prevent the error from happening again, but it will quickly reset your iPad with a minimum of hassle.
Here's how you do it:
At the error prompt, select Settings.
That brings you here, to the Settings screen. Select Usage in the middle right.
You'll see this screen, which shows the space available on your iPad. (More correctly, you'll see what your iPad thinks is your lack of space.) In this example, you can see it shows that I have "0 Bytes Available."
My solution is a reset, but not a complete iPad reset. Instead, I just reset the network settings. Select Reset.
Select Reset Network Settings.
Enter your iPad passcode (if you have one).
Once the network settings have reset, the iPad will come back to your home screen. You should see this message:
Enter your PIN code to unlock the SIM card.
At this point, you will be back to your home screen. But your network (wi-fi) settings will be cleared. No problem, it's easy to reset them in a moment. First, let's confirm that your reset fixed the storage space problem.
See? I'm back up to 40 gig available.
The last thing you need to do is reconnect to your Wi-Fi. Select WiFi and enter your password. And that's it. Your iPad space is back and you're all set.
Note: I see this error return every couple of weeks, but it's a quick enough fix to resolve it. I am hopeful that Apple will provide an official, long-term solution, but until they do, I hope this helps you, too.