Other Slipping out of 5th gear...

Well like the title says my yz426 recently started slipping out of 5th gear back down to 4th. Anyone have any ideas where I should start looking for problems first?
Usually it's the gear engagement dogs getting rounded off. However, it's unusual for it to happen between 4th and 5th. It can also be bent shift forks that don't really get those dogs fully engaged. It could be something as simple as your shifter hitting your case and not allowing the shifter to move all the way.