This is a known issue. Note that it is not specific to Brave — other users with adblock extensions like uBlock Origin are also encountering this issue.
As usual it’s important to remember that this is/will be an ongoing battle between Youtube and ad blockers, so this issue will come back every now and then when they find a way to work around our Shields/ad block protections.
Our web compat. folks are working on this issue presently and we hope to have a solution soon.