Chromecast is somehow buggy the last months for me, too. I use now an open source software combination to workaround this.
On the PC/laptop download and install Sunshine, on the Chromecast open Playstore and install the app Moonlight Game Streaming. Run sunshine on your PC (search in startmenu for it and run it), set an username and password, login with the created credentials and go to PIN (on top), now run the moonlight app on the chromecast and you should see your PC/Laptop, press the Select Button (middle button the remote) when you selected your PC/Laptop and on the Sunshine page on your PC enter the PIN you see on the TV now. Now both are paired and you can stream your desktop or configure other apps in the sunshine webpage (applications also on top of the config page) which you could start on your PC and which will be streamed to your TV.
On the chromecast inside the moonlight settings (the gear icon on the left) you can change the Video resolution, bitrates and much more to fit your needs.
This works for me fine and has less issues compared to Chromecast and you can for example play games from your PC on your TV while the PC stands in the bedroom/work room and you sit in front of your TV in the living room.
