You need to disable the Smart Lock trust agent every time, before rebooting, and enable it again after.
It's a bug which Google seem to have no intention of addressing
Then get a OnePlus or Motorola. The point of owning a Nokia is that you get as close to the original Android experience as possible. No bloat, no skin you don't want, no apps you don't need, just Android.
This is not an issue for manufacturers to fix while they pile tons of crap on top of the stock Android, it's down to Google.
No need for what? You argued that OnePlus and Motorola were superior because they no longer had the issue. I merely advised that you should buy those phones if you wanted everything that comes with them.
I'm saying that the issue is with Android, not Nokia. I thought that was clear. You could have Googled the problem and found a thousand threads on the topic, all related to different manufacturers.