Update the apps on you TV and make sure you are on the latest firmware. Go to the Google Play Store and at the top scroll right to your User Avatar and Manage apps and Games. Update ALL from there. Have a look at what's recently been updated. Maybe there's a new app you have installed that is interfering, I've had that problem. Maybe you could remove all 3rd party apps to find out. Also there's a Android System Web View which always causes problems on my phone, check to see if that has just updated on your phone, if it has either try and find an old one or wait until they fix it, it's usually fast or maybe it's the same on the TV. You could just disable it to see (remember to re-enable it as it's important!) Clear the cache of the Chromecast built in....check to make sure you TV is actually connected to the internet, I hardwire mine as it's faster than WiFi....check on you phone and iPad that your Chromecast app is the latest...and lastly as always...a factory reset. Hopefully something there will help!!
My betting would be it's the Android System Web View app that's just updated on your Phone and iPad or it's a Spurious 3rd Party app you e just installed on your TV...fingers crossed you won't have to do a full reset.
