What causes Kerbals to become brain dead debris?

Jebediah was testing out my new monopropellant lander on the mun. After landing it was obvious that he was some 300 units short of making it back to Kerbin.

I designed and sent a lightweight refueling lander with grapple arms to fill Jeb's lander back up. It was hex-radially designed with interspacing command chairs/monopropellant tanks with grapple arms around a 1/4 orange tank with a poodle engine. These radial command chairs were piloted by brave & stupid white suits who were chosen for their ability to have unlimited suit lights.
Now unfortunately I ran short of fuel while coming into the target area and did a very hard landing.
Luckily the refueler only suffered damage to the poodle engine and 2 of the grapple arms while retaining it's solar panels and SRS. So I decided to roll my way on over to Jeb.
While I was rolling I would lose a Kerbal every once in a while as they fell out of their command chairs. No problem I thought I can just walk em back in.

However, after switching to them they wouldn't move they just stand there and when I mouse over them it breifly says debris!

Normally when I kill a Kerbal they go poof and are normally travelling at a much higher velocity.

Do command chairs cause Kerbals to become debris? If so how does this happen? (like is it from hitting the ground or just being jostled around in a giant wheel, etc.) Would a roll cage prevent this?

Pic of recreation on launch pad Poor Jeb is debris...

Solution 1:

It's true that the command seats cause the kerbals to become debris, as you stated. I have driven rovers many hundreds of kilometers on the Mun and Minmus, and have had this happen many times.

In fact, it seems that just touching the command seat the wrong way can cause this! More than once I've had kerbals standing in the rover collecting science, when the rover starts to roll, causing the kerbal to bump the seat and fall out. Not every time, but sometimes the kerbal becomes completely unresponsive. It seems that the harder he bumps the seat, the more likely the chance of him becoming zombified.

Here's how I revived them a couple of times:

(WARNING! If you don't know what you're doing this most likely is not going to work for you. Back up your quicksave and Persistence files before attempting this!)

1. Stand a fully responsive kerbal beside the zombie kerbal.
2. Quicksave with F5
3. Minimize the game and open the quicksave file with Notepad or any text editor. The quicksave and persistence files are in the Saves folder within your KSP folder. Your KSP folder location depends on whether you're running the Steam or non-Steam version. In any case, it will be somewhere inside of your Program Files (x86) folder if you're running Windows 7. Sorry, I don't know about Linux or Mac.
4. Find the zombified kerbal in the file.
5. Open the quicksave file with Notepad a second time.
6. Find the responsive kerbal.
7. Compare the two and you'll see the lines that declare him as debris. Edit them appropriately according to the "good" kerbal.
8. Save the quicksave file that you edited. Be very careful because Notepad will save it with a ".txt" extension if you don't know what you're doing.
9. Go back into the game and hold down F9 to load the quicksave.

If you've done it correctly, zombie kerbal will be cured. It has taken me more than one try sometimes to be successful, but it works.