Cast to Device - Windows 10

Windows 10 allows “Cast to Device” for media files to network-linked devices (via right click).

I’ve used this before (months ago?) to watch movies on TV (Samsung) via files stored on laptop. Simple process - success!

Last night however I tried this again and about 30 minutes in or so, the connection was lost. The TV screen went black but the movie continued to play on the laptop. The network did not go down. I simply started the file again and we continued the movie. Unfortunately, this happened 2 or 3 more times, without explanation.

Any ideas?

Auto-standby in the TV settings?