Who knows why, but after working flawlessly for 2 months, now my fairly new Philips 65inch Android TV just started failing and crashing alot. The built in Chromecast that was working so well just started refusing to work with any phone/app combination after rebooting the TV and Phones... weird.
Sometimes it's the modem/router the source of the problem, can you check that you have something called "Short GI" turned OFF in settings?, try that and let us know the results.
Unplugg it from the wall for 40 seconds
Try to uninstall Chromecast built-in app so you have the factory app and clean the cache of this app.
Werd. Yeah it seems like I remember it not working one time when I was hammered and then the next morning it worked fine... I figured "awe man I was just high af" - but now I know that for some weird reason it is intermittently working and sometimes not... but this has been days and several resets and no fix yet
Mine did this to me the other day then randomly started working again. Was really strange.