Hello
I have noticed that an ad plays in the video when it is shown in the YT channel title page (I believe it is called the Introduction section).
The ads in the main channel are still blocked okay, but I decided to report this anyway, since the shield obviously has a loophole there.
I am running Brave version 1.71.118 on Windows 10, the components that look relevant are as follows:
Brave Ad Block First Party Filters - Version: 1.0.234
Brave Ad Block Updater - Version: 1.0.8642
I will be happy to provide additional data to the Team should they need it.