Word template files (".dotx") are great for creating templates for other Word documents. For example if I were to create a Word template file called "Agreement.dotx" and I were to double click it, Word will by default create a new instance of the template file as a ".docx" instead of allowing me to edit the ".dotx" file itself.
To edit the ".dotx" file I'd have to open up the ".dotx" within Word specifically by doing "File" - "Open." The purpose of a ".dotx" file is to act a template for a new Word document, rather than to act as a template to be filled in and reused (like a Woodpecker template).
If you want to use a ".dotx" file as your Woodpecker document, you'll have to specifically open up the ".dotx" file instead of just "double-clicking" it, since Word will create a new instance of the template file and your Woodpecker fields will not transfer.
The best way to avoid this is to save a copy of the ".dotx" file as a ".docx" file and then distribute and use the ".docx" version, as the Woodpecker fields will be saved and will transfer.
In short, the recommended way to create and reuse a Woodpecker document is by using a ".docx" file and not a ".dotx" file.