For anyone with the same problem (helper tool crashed...), there is a
problem with the jamf framework, blocking or killing the helper tool. I
changed the command to jamf removeFramework; "/Applications/Install
macOS Mojave.app/Contents/Resources/star...
We currently have a wipe & refresh policy, we install 10.14.5 Mojave to
Applications and run the command: "/Applications/Install macOS
Mojave.app/Contents/Resources/startosinstall" --eraseinstall
--newvolumename "Macintosh HD" --agreetolicense someti...