If you configure Forms to store something in a path that represents an existing folder, and don't configure its metadata (such that it is set to "None" in Parent Folder Fields), Forms removes the template of the folder.
I can't tell if this is intended or not, but it feels pretty bizarre to me. I can't think of a situation where one would want to simply remove the template of an existing document in the repository (and not assign a new one).
I think when it is set to "None", it should keep the current template unless the user specifically configures it to be removed (maybe with a checkbox).