And the common theme is - cycling. As Stryd note, if you use it as running power using their app it is not a problem. So yes, Garmin have something to fix, but for those using running power, the workaround appears to be to use the Stryd app.
As an aside, I'd be interested to know if this affects only 3rd party power meters and not the Garmin Vectors, or all power meters.
I don't think it's quite that bad.
?
I have 5+, 6.0 firmware, stryd latest sw, and no power irregularities looking at recent runs.