I have installed ubuntu 18.04 in my dell inspiron 3551 and having problem during shutdown/restart. The laptop gets hang and the shutdown does not completes successfully.
Also when I move down the flap of my laptop and move it back the system gets hanged on the same screen I left it.
In both cases I have to forcefully turn down my laptop by pressing the power key for few secs. Tried adding GRUB_CMDLINE_LINUX_DEFAULT="quiet splash acpi=force" in the grub file but nothing changes