“Failed to execute default Terminal Emulator: Input/output error”
I recently ran into this problem with xfce4-terminal, I have around 7 or 8 desktop environments installed and selectively upgraded xfce4.
After spending an hour trying to fix the problem here’s what worked (total accident).
I was installing termite (another terminal emulator), and it installed vte3-ng and removed vte3.
I tried reopening xfce4-terminal and it worked like a charm.
Hope it saves you some time!