When cloning assets you should always clone from the original asset. Say that you have email A, and you clone that original email into version B, and then clone version B into C, and clone C into D, etc. There is potential for asset corruption when clones are cloned repeatedly.
It is best to clone the original rather than making clones of clones. When creating assets, whether they are individual assets like emails or complex assets like programs, set one as the master asset and clone all copies from the master.