Even more galling is I have yet to figure it out. I just have to wait until, sometimes, after waiting long enough, it starts working again. Like I completely closed every screen tab and screen and the terminal session and iTerm, and when I logged back in it was still broken—yet in just the time it has taken to write this, it has resolved itself without explanation and works again.
After all these years I have no idea how terminals work. It's still completely high magic and I'm totally stuck whenever it breaks. It doesn't help that it's completely impossible to search the internet for keystrokes.