Existence of diffeomorphic but not 1-isotopic ribbon surfaces

A ribbon surface is a ribbon surface carried as a $2$-dimensional sub-$2$-handlebody of a $4$-dimensional handlebody. A 1-isotopy is a $(1,2)$-deformation between ribbon surfaces, allowing embedded $1$-deformations of the surface together with ambient $2$-deformations of the handlebody. The ribbon-surface conjecture. There exist ribbon surfaces that are diffeomorphic but not $1$-isotopic. This would show that diffeomorphism of ribbon surfaces can differ from the equivalence relation generated by the prescribed surface and ambient handlebody deformations; the source provides no resolution.