Erroneous characters while in Emacs M-x shell

[nickpapadonis]

I created a video of the issue: https://www.youtube.com/watch?v=oPERMapfapo

Emacs 26.1, ssh 93u+, Debian Linux 10.

^L's are output while moving the mode line in the middle of two buffers. This behavior does not occur using Emacs as a shell.

How can it be diagnosed if the problem is ksh or Emacs?

Thanks

[saper]

Thanks, I could reproduce it using emacs 26.3 on FreeBSD 11.3 with ksh93 93v- just by resizing emacs frame (with shell-mode being the sole window).