Edit subtitle: "Motorised automatic bollocks to prowl Iberian fields DOWNHILL"
Stairs? They have an inclination of typically 40%
Any incline above 20% will already stop these balls, there's just not enough space inside the sphere to move the centre of mass sufficiently. So for a golfball-sized sphere, a matchbox is insurmountable; for a football-sized one, a regular kerb (or a furrow in a field, more to the point);
Yet a staircase is laughed at by an apartment-sized spherebot (though I may have played too much katamaru damashii.