For Brave. (might be a their end/chromium issue)
When flags Experimental Web Platform features ( chrome://flags/#enable-experimental-web-platform-features ) +
Adaptive global tone mapping ( chrome://flags/#hdr-agtm ) is enabled
The new media player hitches the entire webpage as it struggles to load, and also causes the player to lag out and buffer repeatedly.
Problem was fixed after disabling flag.
edit. hmm tried a clean portable version of brave and worked fine... even with the flag enabled
Edit 2 boogaloo. Enabling both Experimental Web Platform features and Adaptive Global Tone Mapping causes issues reported (both needed otherwise worked fine with either, one at a time)