(ln response to a now removed question as to why concrete slabs failed and small buildings got airborne)
Case one, on a more level area, the primary cause was insufficient ground clearance (and grassed soil tends to build up over the years, making it worse). Result was rising damp in the outer walls. Case 2, the house we currently are in, the guy building it in 1981 had two sheets of polythene to go under the concrete. He lapped them by a foot or so and gaffer taped it. Water pressure from the slooe above eventually found a way through resulting in a patch where any floor covering quickly rots. Yes it can be done right, but not on a budget.
The shed was a couple of learning processes. 1) complying with "relocatable" requirement to avoid need for a building permit doesn't mean you can't have any attachment to the ground. And 2) To avoid a monopitched roof acting as a lift-generating wing it needs to be pitched at 18 degrees or greater.
Edit: after sleeping on it, it has occurred to me that the solution for any high-mass earth-based structure (rammed earth, earthbag, earthship etc) is to create a raised platform under it. Roading mix from a quarry about 25km away is $15/m³ plus the cost of trucking it and compacting it. Minimising platform costs would dictate site location - more central on the section than we would otherwise like.