I have a 1st Generation Chromecast dongle that has stopped working since the 11th August 2022 update that was applied to the 'BT Sport' Android App.
When I try to cast any of the 'BT Sport' channels, the 'revolving circle (of doom)' sits there for a while and then I get the error code 'VC526'. I have tried rebooting / factory resetting / re-installing of the Chromecast and its settings several times, all to no avail!
The Chromecast will happily cast other streaming services such as 'BBC iPlayer' without any problems, so it is definitely a 'BT Sport' app issue.
I also have a '3rd Gen Chromecast' dongle that currently works, but I am wondering how long it will be before that also stops working!!! Temporarily I have put a stop to 'auto update' of my 'BT Sport' app in the hope that will avoid the inevitable failure of the 3rd Gen after some future update.
If it turns out to be that there is no solution to my problem, I will most likely cancel my 'BT Sport' subscription.