I might be wrong but I think the only way you can sort of make it "stack" is by being the caster of Warding Bond. The target of the WB gets resistance against all damage types and transfers the damage they take to the caster of the bond, if the caster then also has resistance against a specific damage type they should be doubly protected, but only against the damage they soak from their ward. (Chain-casting WB doesn't work afaik.)
That is most certainly not how is this supposed to work.
