so yes, that's what's causing the issue. I don't think I agree with the importance High, though. PackageKit is not normally used for upgrading, only for installing and removing packages. You have to manually force this by using pkcon, hence it should be Medium I think.
packagekit postinst is restarting packagekit:
deb-systemd-invoke try-restart 'packagekit- offline- update. service' 'packagekit. service'
so yes, that's what's causing the issue. I don't think I agree with the importance High, though. PackageKit is not normally used for upgrading, only for installing and removing packages. You have to manually force this by using pkcon, hence it should be Medium I think.