I added this to the T-Mobile Community help section:
I changed from Cox to T-Mobile internet. The download speed in exceptional. The Alexa transition was smooth once I added 2.4G to my T-Mobile router. I named the new 2.4G the same as the Cox name with the same password, every device moved over as hoped. My home is automated with multiple plugs (7) and Feit Bulbs (30). Once setup everything worked for a short time. Then the bulbs would drop offline at random. The plugs always work. To reset the bulbs all I need to do is turn off the power to the bulb and turn it back on and then they are connected and work with Alexa. I have tried to find a pattern (like time of time or phase of the moon) but there doesn’t appear to be a pattern. I have via the Feit App set all devices to update the firmware automatically. Also, setup all Feit devices to push a notification when they drop offline; there are many pushed messages in the Feit app but again no time pattern. I have an open ticket with Feit and have tried all their suggested solutions - nothing has worked so far.