Your comments

3 years later and people still use this? I forgot this even existed :)

I've stopped using sidewise. I just suck all the tabs into Onetab when it grows unwieldly. Now I don't have to worry as much about the memory bloat of the browser
Incidentally, the problem seems to go away when you turn on debugging...
I'm experiencing the same issue. I can get it to calm down sometimes but it often just flashes focus between the sidewise sidebar window and the chrome window.