I have 2 KC420WS cameras that show "net work unstable" ONLY ON MY PHONE and only in the TAPÓ APP.
EVERYTHING WORKS FINE on My old phone/ipad and my husband's phone and iPad are just fine too.
These products have worked fine for a year and I can guarantee they have good signal and our internet is stable. And the tapo app has always worked fine for me. 
I made sure my app was up to date as well

as the firmwares up to date 

then I reset the router (even though it worked fine for my husband). SAME MESSAGE 
I turned off my phone and let it reboot - SAME MESSAGE 

I hard reset my phone.  SAME MESSAGE 
I finally deleted the TAPO app and reinstalled it.  SAME MESSAGE 
Any suggestions are appreciated. I don't want to have to use 2 apps to see my devices and it's strange that everything worked well on my old phone and that it doesn't work on my new phone.