Update Taxonomy Term Parents action creates duplicates

First, this module is great, thank you. I specifically needed this module for the update action. The action works as advertised and saved me a lot of time.

There is one issue, however. When the update action adds ancestor terms on an entity, it doesn't appear to check that the term already exists before making the addition. Or perhaps it's the case that if there are two terms that have a common ancestor, it is adding that term twice. For example, say a node currently has a child term and its parent term. They have a common ancestor -- for the child term it is a grandparent; for the parent term, it's a parent. It may be adding the common ancestor term twice. I'm not sure.

What I do know is that after used the update action on a set of nodes, I used the Devel module to inspect the values in my taxonomy reference field on the nodes and there were, in some cases, multiple instances of the same tid. It seems like somewhere in the module code a check needs to be made or some deduplication should be performed.