Sharing facial animation between different characters (same hierarchy) with joints

Hi everyone, I would really like to know in a nutshell, is there a way to retarget characters between one another when they share the same hierarchy and joint orientations. Before you answer, let me elaborate.

We have 5 different characters, all have different proportions between limbs, but they all share the same skeleton.

We want to be able to use character 1 and propagate the animation to 2, 3,4, and 5.
We would also like to use character 2 and propagate the animation to 1, 3, 4, and 5. Etc… for all the rest

The body retargetting seems to work ok, it’s only the facial animations that don’t appear to work. They only seem to work if we animate on the (“Initially created skeleton”). That is, if we create skeleton 1, and derive all the others off that one, and animate skeleton 1, then all the others get an accurate representation of the facial joint animation offsets (if we use the retargeting method in the skeleton called Orient and Scale).

However, we cannot author animations on character 2, and then import that fbx animation onto the created skeleton (which is as mentioned above, character 1), without the facial animation breaking and going screwy.

Is there a workaround for this? Has anyone else experienced this issue?

Many thanks