Ive spent more time than I care to recall trying to figure out what is causing this. Im 100% sure its a conflict caused by the Razer Synapse software. Yes adjusting the tracking for the razer product with the synapse software will fix the problem, but if you want to continue to use a magic mouse, you are boned.
I was actually having my tracking revert during normal operation, not just when I restarted OSX. Since I do 100% of my gaming these days with bootcamp I just completely uninstalled Synapse from OSX and problem gone. I think really what needs to happen if it has not already, is this thread needs to be linked to a Razer support thread that their people will see, cause again, I'm 100% Razer and their notorious shoddy programming is causing this issue.