I can live with it, but it could signal trouble.

On 2 near identical Lubuntu 18.04 LTS installs, to enter Veracrypt passwords
- on the notebook I can move the cursor and use backspace and delete to correct my typing
- but on a desktop PC I can only use the mouse to select parts of the password and type over them.

This has been going on for years.

Tried reinstalling Veracrypt and dumping its configuration files.
No change.

No other applications exhibit this behaviour.
it happens only in the Veracrypt password dialog.
What could be the cause?