It sounds more like the fork (#4 in attached picture) to the reverse gear is bent not allowing the gear to fully engage. Before removing the side cover to the reverse gear housing check the check ball bolts/cover (see arrows in the attached picture) that may have come loose and keep the fork from moving far enough to keep the reverse gear in place.
If you want to remove the side cover, the battery, starter, stator/stator cover, oil and speedometer cable all need to be removed to get to the reverse gear cover.
Then check to see of the fork is moving enough to move the reverse gear in to the proper position.
Bill