We've disabled Chromecasting for Gear VR for some people due to a known issue. We are working on a fix and hope to have it back up for everyone shortly.
Could you inform us as to what known issue is being worked on? If it helps, I did some of my own analysis during the brief time when Chromecast was enabled on both my S7 and an S8 I had on hand. The two issues I discovered were related to audio and heat output.
For the latter issue, someone else commented that being able to choose a lower streaming quality (e.g. 480p15fps) would help a lot.
S7 Exynos Nougat. 2017 Gear VR. Public test channel.
Any updates here? It also appears that when enabling simple screencasting via Google Home, Chromecast works great UNTIL you launch a GearVR app and insert into the headset. Image appears, but then immediately freezes. Other VR-based applications (Google Cardboard, etc.) seem to work just fine so far - both video and audio cast successfully.
Ideas? Suggestions? Workarounds? Even and interim hack would be much appreciated.