Issues With Chromecast topic

Hi All, I've just joined this forum so apologies if this question has been asked before..:o

I recently bought the chromecast and so far loving it! But lately whenever I try and cast a tab from Google Chrome to play a video (not Youtube), the video plays fine, but previously using Win+T I could toggle between the tab (currently playing full screen video) to another browser and use it simultaneously. I now find this is impossible, and not sure what the issue is. If I toggle between tabs, the video playing also minimizes..:confused:

Any help would be greatly appreciated and not sure if I have managed to explain it properly!

Thanks in advance..:)