Just the use of the Sensor Trigger feature with the activity. Although…I wonder if that shows up by virtue of the fact that I have paired the Harmony Hub with the ST hub. I’ve had a consistent issue with being able to connect ST and Harmony in both directions. Harmony can control ST devices, but ST can’t control Harmony. There’s a whole 'nuther thread about that issue 
Anyway, perhaps there is a lower level connection and my ST bad behavior is dragging the Harmony Activity along with it. The whole thing seems a little convoluted and mysterious. It’s all great if it just works, but when weirdness like this happens, it’s hard to unravel. I did find another thread that seems to describe exactly my issue.