I have 4 HS220's that keep restarting themselves every 30 seconds.   Each one is connected to the neutral wire correctly, as well as load, line and ground.  

The odd thing is, they don't restart themselves until I go through the setup process and add them to WIFI. Before setup, they work fine and don't restart themselves.

I have 4-5 other HS220's in my home that never had any issues.  The only thing that's changed is that these were just recently ordered, and my wifi router has changed (although the old switches connect perfectly fine to the new ASUS AX11000).