The rear fin pops out. I can't seem to get the Allen screw tight enough and fear stripping it if I torque it too much. the hole where the rod enters the unit is getting increasingly elongated due to it coming apart while under pedal power. The mirage drive also fails to remain locked into the hull during use.
If your mast hole is elongated at all, the Allenhead screw will no longer be able to hold it in place. Check your other sprocket while you're at it. You have two options.
1. Replace the sprocket. You can replace it with the same fitting (using Locktite Blue on the Allenhead to keep it in place) and risk the same result down the line or try the new threaded sprocket and mast and solve your problem. If you do that, just remember to use Locktite Blue to secure the mast so that it doesn't unscrew (standard factory procedure).
2. If the hole isn't too widened, you should be able to epoxy the assembly together (including the Allenhead screw) and get a good result. You have nothing to lose by trying it since you would otherwise throw the old sprocket away.
If the Mirage Drive is unlocking, especially on the Starboard side, your right heel is probably accidentally unscrewing it. If so, you just need to be aware of it. There isn't much you can do about it except change your foot position.