By the way, I'm not an admin, moderator, or involved at all in the behind the scenes work on this forum, so I could be wrong. But, it sounds to me like this is an issue that Brave would need to resolve.
I had run a forum years ago using the same software this forum uses, and basically, as an admin, you don't really have much control over how to fix technical bugs or anything of the like. More complex stuff like that would need to be addressed by either the developers of the forum software (phpBB) or developers of the browser. Seeing as how these forums work just fine on all other browsers, I'm going to assume that this is something the Brave developers will have to fix. Also, like you, I've had a few minor issues with a few other sites using Brave, but I still use it as my main browser.