So this is most likely a re-targeting issue. If the re-targeted skeleton does not have the same proportions as the original, sometimes things like this can happen. It seems to be that the Retargeted character is using the same Bone Translation Data of the original animations, causing the character to be misshaped. Thankfully this can be pretty easily changed. In the skeleton asset under the Hierarchy window, click on the Eye icon near the bottom, and under the options section click “Show Re-targeting Options”. Once these are displayed you can choose whether you want to use the bone translations of the original animation data, or just use the rotation data and keep the translation data of the Re-targeted skeleton.
You can read more about this here - https://docs.unrealengine.com/latest/INT/Engine/Animation/AnimationRetargeting/ Setting Up Retargeting heading.
Animation Retargeting can be pretty confusing, so just stick with it and you will figure it out. Remember though, If you are able, It is always better to custom make the animations for your skeletons (or retarget in a software like motion builder), that way you have more control over the final result, especially if the character is holding an item with both of their hands, as different proportions can cause hands to be miss-aligned.
Hopefully this answers some of your questions, or at least points you in the right direction.
Thanks for the reply.