I suspect the issue here is that when the document has been reverted to word, and changed back to PDF a new layer of fields are added through Acrobat without the required settings on the fields (i.e. locked fields).
You can either apply the fields to the word document as a text tag where you can specify the formatting and type of field you are adding (i.e. required, who is the signer etc.) or you can save the original layer of fields in their position as a form field layer. You can then add the form field layer on top of the amended Word document. To do so, please go to: https://helpx.adobe.com/sign/help/reusable-form-field-layer.html
Hope this helps! Let me know if you have any more questions