Last month, Google announced that they were going to be releasing an update to Google Play Services to address a network issues caused by the service. The issue would essentially flood your home network with packets as your phone would continually try to connect to Chromecast devices on it – your Chromecast and Google Home devices specifically.
The update, at the time, rolled out into the beta for Play Services but today is rolling out to everyone. The new build is version 11.9.75 and should be coming to devices over the course of the next few days.
For those that haven’t encountered the problem (good!), it comes down to Android devices on your network as well as Chromecast and Home devices. Essentially what was happening is that Android devices on the same network would see the Cast enabled device and flood your network with packets. That would cause slowness or instability. It was effectively an internal DDoS attack.
Originally, the thought was that the problem was associated with Google Home itself, specifically the Google Home Max which had just been introduced when reports of the problem began surfacing. Google engineers quickly determined however it was a Play Services issue and began working on a fix.
Generally, Google Play Services updates happen quietly behind the scenes but you can always check to see if you have this latest build installed. Go to Settings>Apps & Notifications and find Google Play Services. On the App Info page for it, at the bottom, you will find your version number.