@Carl Here's an update: I installed a second 3-way switch for another light (not on the same light as the first switch so only one switch in each circuit). I ended up having the same issue as the...

@Carl OK, I double checked the connection. The switch is definitely connected to the Line, not the Load, side. I also deleted, then reinstalled the app. The firmware of all the devices is up-to-date....

I replaced one of my dumb 3 way switches with a HS210 smart 3-way switch. Everything seems to work fine when I manually press either the HS210 or the other dumb 3-way. However, there seems to be a...