Please see our forum post about the Ubuntu 18.04 bug and our suggested workarounds: https://discussions.agilebits.com/discussion/90011/lock-screen-issue-1password-x-for-firefox-on-ubuntu-18-04. Sadly the bug is in the operating system and affects all browser extensions with password fields in them. We have reached out to Ubuntu and the ibus project and hope a fix is coming soon.


Update:
Ubuntu has fixed the underlying issue that was causing focus issues with the 1Password popup and many websites with password fields in Firefox.