@Madtom 

I just went through the same thing... actually still going through it but I think I have at least somewhat of answer. I have multiple HS210's in my house and all worked great on initial install except one. I would have to click the button in the app multiple times to make it change state and it rarely showed the correct feedback state. I use Google Home and Home Assistant and all had the same response issues. 

The answer I have settled on is the light having issues has long traveler wires (wires running between switches) and a small load of LED lights only. I think the long traveler wires and small load is creating some capacitance on the travelers giving the controller in the switch fits about it's current sensing. I tested this theory by placing a resistor across the traveler wires on the switch to short the capacitance. Success. the switch then operated and reported correctly. The problem was I only had a 1/8th Watt 10K ohm resistor on hand and when the lights were off it bled too much current to the dead leg and burned the resistor up when the light was off for more than a few minutes. 

For the short term I unhooked one of the traveler wires on the smart switch and capped it with a wire nut. I then switched the dumb (standard) 3-way switch until the light turned on. Now the smart switch works and reports correctly. The other switches in the circuit cant be used now or the circuit won't work but at least the smart switch works.

The more permanent fix is getting a larger resistor to place parallel across the travelers that will limit the current draw or to add some kind of big inductive load (tungsten bulbs) to the circuit. I'm going to try a 1 MegaOhm and see what happens. I can't or don't want to change my lights as they are built in LED can lights.

Hope this helps.