What is the safest way to shut down a Mac which is stuck at the screensaver?

I use a MacBook Pro for work. According to my workplace's policy, when I leave my desk, I lock the screen. There's a bug in MacOS High Sierra where sometimes when I come back and unlock the screen, the screensaver is showing and can't be dismissed. The laptop is therefore unusable.

The only way I have found of getting back into my mac is to hold the power button down until the laptop shuts down. But this isn't a safe shutdown; if I have any Parallels VMs running they are usually corrupted and I have to restore them from backups.

Is there a safer way shut down, or otherwise get back into, my Mac? If so, what is it?

A couple potential ideas:

1. Try to avoid the Screen Saver Bug: Turn off the screen saver (set it to “Never”) and just adjust the Energy Saver to turn the screen off to prevent burn-in. You can still lock the screen with ⌃⌘Q

2. Alternate Login Methods: If allowed, turn on Screen Sharing and/or Remote Login in System Preferences » Sharing and see if you can login with your phone using ssh or vnc (I recommend Prompt and Screens, respectively).

3. Sleep Instead Of Lock: Enable a “Hot Corner” to put the Mac to sleep instead of just locking it with the screen saver. Not as convenient as just locking it and walking away, as it will take a little longer to wake from sleep, but if it doesn't trigger the bug, it would be worth it, perhaps?

I would recommend you to have a look at Apples own help pages, i.e. https://support.apple.com/en-us/HT201236

Specifically these two are of use:

Option–Command–Power button or Option–Command–Media Eject : Put your Mac to sleep.

Control–Shift–Power button or Control–Shift–Media Eject: Put your displays to sleep.

Putting the mac to sleep usually clears issues like the screensaver issue. Sometimes I've even had the luck of just putting the display to sleep clear the issue.