It is interesting to point out that the mobile connector is sealed shut. If you want to open it and look inside you can't just unscrew it, you need to use a circular saw and make some deep cuts.
I agree that it should not be considered waterproof, and have had issues not only with "rain" but also with humidity and rapid temperature changes (30F -> 70F -> 30F within a few days). I kept it out of the rain, but still outdoors and it had issues.
I have a theory that it has significant problems with internal condensation, and that it is intended to be airtight and water tight. Whatever moisture is trapped in there at the factory or which leaks in can never leave.