Liquid doesn't mean just water. I think what op was getting at that the molten core of the earth is in liquid(-ish?) form, thus the water balloon idea.
256GB seems fine for me. I tend to have everything in the cloud in case I lose or damage my phone so actual use of the "hard drive" is fairly limited. I don't really like playing such games on a phone and that's the only scenario I can think of where I'd need so much space.
I'm not an expert, so maybe someone can say if this might be a valid theory, but could it be that the weight of the water for a prolonged period has caused some pipe to come loose or something like that?
Liquid doesn't mean just water. I think what op was getting at that the molten core of the earth is in liquid(-ish?) form, thus the water balloon idea.