This may just be me and because I am using the nightly build, but for the last few days I have noticed that the sound stops playing on headphones when I switch tabs.
I did some research and other people had this problem as well. The solutions they posted didn’t work for me. However I did find something that works.
If you go to the three lines icon where you can go to your settings, then click on settings and then click on system. You will scroll down and see this in the picture above in a section called Performance.
One of the solutions was to turn off the Memory saver, but that didn’t work for me. What worked for me is to add the www.youtube.com site as active which is easy to do if you are already on that tab. It will give it to you as an option. Once I said to add that as always active, then the sound doesn’t cut out on headphones.
I suppose that Brave did this to save energy and resources assuming that when someone isn’t looking at a tab they don’t want the sound. It is a fair assumption but wrong. Try not to assume things, as Reacher says, Assumptions kill.