Sharepoint metadata required to be filled in after editing, even though it is not a required field

I have a form in Word format, which uses Document Properties as fields. These forms are located in a Sharepoint library. Some of these document properties are Sharepoint metadata from the Sharepoint columns associated with the document.

None of these document property fields are mandatory/ required.

When I open the template, the fields are blank and I can save the document. Even after editing some of the fields (some fields are texts, some are dates etc.), I can still save the document.

However, if I try to go back to remove the entry to one of the previously filled in Sharepoint metadata document property fields in the Word document, so that it will now be blank, it gives me these errors: "To save to the server, correct the invalid or missing required properties" and "The length of this text must be at least 1 characters". There is also a red dotted border around the field.

If I check under Info - Show All Properties, none of the properties are marked with an * to show that they are required. However, the fields that I have now made blank have a red box around the "Add text". It will not let me save until I add text to it.

I tried with a few test documents, in different Sharepoint locations. I am seeing the same issue at each location. I tried creating blank documents and added a Sharepoint metadata field as well as a default word document property field (e.g. Author). The same issue each time - If I add data to the Sharepoint metadata field, I can save. Then when I try erase it, it will give me the previously mentioned error and will not allow me to save onto Sharepoint until I enter data into the field. For the Author field, I could add data, save, remove the data in the field, and save again with no issues.

Another scenario tested as well with the same results - Sharepoint Metadata fields "TestA", "TestB", "TestC" added into the Word document. Add data for "TestA" and "TestB", and do not touch "TestC" (leave it blank). There are no issues saving. If I go back and try remove the data in "TestA" for example, it will give the error and will not save.

Thank you in advance.