Windows 98/95 DOS prompt - cursor jumps around

I saw this interesting bug a while ago but I didn't know how to reproduce it reliably until now.

Open DOS prompt on Windows 98/95. If you give your keystrokes enough delay, the cursor loves jumping backwards and does interesting things. What could this be?

Here's a little gif demo. Grab some popcorn.


I'll just dump a couple more observations...

You can see that when the glitch occurs, the previous command / stdin is partially reused:


On Windows 95, reading from console stdin (via `type con`) illustrates this:


On Windows 98, reading from console stdin (via `type con`) closes abruptly with random artifects:


Notice how the garbage text jumped back into the previous line. It's supposed to look like this: (typing the exact same thing in VirtualBox)