I can reproduce this problem with a guest session, so it isn't due to a particularly strange configuration.

  1. Start a KDE session
  2. Open System settings and go to Desktop Behavior/Accessibility
  3. On the Activation Gestures tab, disable "Use gestures for activating sticky keys and slow keys".
  4. Enable "Show a confirmation dialog whenever a keyboard accessibility feature is toggled".
  5. Open an xterm (not konsole)
  6. Run this command to ring the terminal bell: perl -e 'print pack("C",7)'
  7. A dialogue appears reading 'Do you really want to activate "Slow keys", "Bounce keys", and "Mouse keys"?'
  8. Select "Deactivate all AccessX features and gestures".
  9. Press the "No" button to close the dialog.
 10. Run the command to ring the terminal bell: perl -e 'print pack("C",7)'
 11. The dialogue appears again.

I would expect the system bell to be rung without generating a dialogue.

Step 6 can be replaced by pressing the backspace key or tab twice or a variety of other actions which cause xterm to ring the bell.

A workaround for this bug is to disable the confirmation dialog which was enabled in step 4.  I don't think there's any side-effect of the workaround.