I'm a bit lazy and don't really want to test with an other browser.
But I have one last thing I have discover.
I have this option checked:
And when brave browser is restarting it is set to start with last state so with like 7 windows and dozens of tabs by window.
I think the issue is that Groupy is starting auto grouping brave windows simultaneously on multiple windows then grouping those group together here is an exemple of what I thing is going on:
1- Windows A,B,C,D,E,F,G of Brave are opening,
2- Windows A,B,C are grouping together simultaneously Windows D,E,F are grouping together
3-Then Quickly all groups are grouping together creating one big Group with Windows A,B,C,D,E,F,G. There I think previous sub group are staying "alive" in some way.
So when I encounter the issue I ungroup the window that I have the issue with and regroup it with the group and the issue disappear till I restart my computer.