Lighdm breaks suspend ability on nvidia proprietary driver

[Yanpas]

I'm using xfce with light-locker and lightdm-gtk-greeter. Suspend action in xfce causes the screen to lock. After a few requests to suspend the system - suspend becomes broken. I'm unable to launch it again. "systemctl suspend" outputs the following: "Failed to suspend system via logind: There's already a shutdown or sleep operation in progress". If I run systemctl shutdown -f the system goes suspend first, than I wake it up and it shuts down.

Similar report: https://askubuntu.com/questions/743231/after-sleep-state-pc-with-xubuntu-doesnt-let-me-shut-down-the-system

I'm using arch linux with kernel '4.13.8-1-ARCH', systemd 235 and nvidia 387.12-2 driver.

The bug reproduces when using both nvidia proprietary and lightdm. BTW lightdm is buggy with nouveau too, but in another kind of fashion: after resume I see the black screen and I need to switch to some different VT and then back again to VT 7 to see anything on the screen.