[Users] suddenly message editor toggles to overwrite mode

[Pierre A.]

Dear Claws Mail users,

I use Claws Mail 4.3.0 in Manjaro Gnome.

Sometimes, while composing a message, the editor toggles to overwrite mode.

Why? Did I touch some key involuntarily?

How to toggle back to normal insert mode (apart from restarting Claws Mail)?

When Claws Mail toggles to overwrite, gedit does not, so I guess the problem is in Claws Mail, not Gnome.

Sometimes Emacs also toggles to overwrite, maybe because I type some shortcut involuntarily and I know how to toggle back.

Best regards.