Strangely, I had a similar problem but it was only with one specific website - my bank website (rbcroyalbank.com). At some point, it seemed to fix itself and then it came back. I think the problem is related to RBC using non-standard code. Because the problem recurred when they undertook a website re-design. I haven't had it with any other issues.
If you post a couple of the websites you're having trouble with, I could check them in my version of Brave.
This post should be under Support assuming you want assistance and aren't just pointing out a problem.

Either way, I'd like to help if I can so just let us know if you want to fix it.
1. I'm using Linux Lite (based on Ubuntu 20.04), what are you using?
2. And do you have any other browser tabs open when it happens?
3. What extensions are you using?
4. Have you tried running the browser after turning off all the extensions?
Maybe we can find overlap. And do list at least 1 or 2 of the websites you are having the issue with if you don't mind, so we can test them.