Yes, if you close the right instance, it stops. but there doesn't seem to be any correlation with whatever page was in that instance. I've also had issues with

Yes, if you close the right instance, it stops. but there doesn't seem to be any correlation with whatever page was in that instance. I've also had issues with an instance suddenly using 20-50% of the CPU for no reason. Chrome is now my primary browser, but this one issue has made me consider switching back to Firefox.