I’ve added three images to this post and most of the explanation is in the description of those pictures. However, to quickly recap.
When I set up the Aim Offset everything looks as it should, but as soon as it is blended/added with the rest of the animation it freaks out completely. It looks to me a bit like the animation values have simply been added to the standard pose instead of just replacing the values/blending with them.
What could I try to do to fix this?