Apple Watch unlock in clamshell mode often fails

Unfortunately, this didn't help.

Is this a known problem and this is the known solution?

Or is this an unusual problem and this is general advice for unlock-related problems?

Note that this is not a new issue -- I first reported it last September but has been going on for a while. Note also that it's intermittent, but I can't tell if it's really "random" or I just haven't been able to track down the cause...

In any event, how can I make sure this is reported as an actual bug?