Sonos App keeps dropping my coonect

Factory reset is not a cure for almost all issues, it kicks the can down the road and erases diagnostic data Sonos could use to help you.

You might try a solution that has worked for others, assign all Sonos a DHCP reserved address. Once done power down all Sonos and reboot the router. Once it is up and stable power up the Sonos.

As near as I can tell, Spotify and Sonos use two different methods to ‘discover’ speakers on your system. ​@Stanley_4 ‘s suggestion is a great one, but I’d also perform a general network refresh, by unplugging all Sonos devices from power, then rebooting your router. Wait two minutes, then plug back in your Sonos. Wait another two minutes, then test. That might assist, without the entire learning process of assigning reserved IP addresses, but certainly isn’t as permanent a fix. At least you’d get a refresh of the firmware in your router and the Sonos, in addition to a fresh set of non-conflicting IP addresses. 

Have you updated your Android device?

Thanks Staley & Bruce, I'll try these suggestions.

Android is updated, the issue was the same on my wife's iPhone.