Protect/save graphics corruption DocIO libraries 18.1460.0.42 Completed

I have found that many times that loading and saving a Word document using DocIO library methods may corrupt some graphics in the saved file. As a test example,  I have attached two files. "doc_before.docx" is the original Word file before processing. "doc_after.docx" is the saved file using DocIO method. I kept the operation very simple for the test:
`
in code, loaded original file "doc_before.docx"
in code, removed all protections from the file:

document.Protect(ProtectionType.NoProtection);
document.AcceptChanges();  // omission does not affect result.
document.Save(path,doctype_matching_original_file):

`

View saved document in Word. The graphics are altered compared to original file.

Considerations: The graphics are color. 
The problem is not peculiar to the Protect method only. Saving documents after other changes, or no editing changes at all, may also show missing or corrupted graphics. Gray scale images may or may not be affected, but seem to be more consistently reliable. Sometimes they simply seem to be missing from the result.