I left the sync chain and rejoined, hoping this would fix my issue.
Unfortunately it hasn’t 
Apparently the tab for brave setting is frozen. I can still use Brave in other tabs. CPU usage looks normal. But sync doesn’t work
Edit: after restarting brave I was able to tick the sync everything box, but it’s not set/saved it’s gone after another reboot.
I ended up deleting my sync chain and creating a new one.
And I noticed that some computers are listed twice. Is this normal behavior, and is it ok to just delete the oldest listing?