Multi Window on my Samsung Galaxy S8 plus no longer works properly.

[Android Central Question]

Starting yesterday, my Galaxy S8 plus is refusing to open two windows of the same app.
I use Brave browser daily in multiple windows, so I can let one page run while loading or executing stuff on the other.
Using tabs does not work, as the tab stops executing when in the background, but multi-window worked fine until yesterday.

Now when I open Brave, (I also tried Firefox with the same result) in one window, then try to open another Brave, it just overwrites the already open page.

This makes multi-window pretty much useless.
Anyone know why this is happening, and how to remedy it?

Thanks,
David