Newton strata in the loop group of a reductive group

We generalize purity of the Newton stratification to purity for a single break point of the Newton point in the context of local $G$-shtukas respectively of elements of the loop group of a reductive group. As an application we prove that elements of the loop group bounded by a given dominant coweight satisfy a generalization of Grothendieck's conjecture on deformations of $p$-divisible groups with given Newton polygons.