Can a font become 'corrupted,' and how to replace?

This refers to MS Word from Office 2019, running under Windows 10 Pro.

I have a somewhat large (10MB) Word .docx I've been adding to as time permits.  It has text, illustrations, pictures and captions for the pictures in text boxes.  suddenly, when I open the file, some of the captions are garbled.  The font I used is Arial 10pt, bold and regular.  The bold is just fine, the regular is garbled.  However, if I highlight the garbled text and change it to bold, italic or any other font, it appears just fine.

Here is an example of what I'm talking about.  First the .docx as it appears on my screen:

Then if I highlight that garbled text and change it to Bold, or any other font, it looks good:

If I change point size the problem persists.  It's just Arial Regular that garbles, and only in this document, and .  Other .docx files using that same font display fine.  Also, I can take this file and open it on my other computer, which is running Office 2010 under Windows 10 Pro, and it opens properly. 

I do have Word programmed to embed non-system fonts in the document, so I'm assuming that Word is fetching Arial Regular to display when opening the file on this computer, and that my other computer maybe has a good Arial Regular installation, which is why it looks good there.

Something else I just noticed, referring to the two screenshots that follow.  Other 10pt. Arial Regular that was NOT in a text box seemed okay in this document.  But on close examination, the kerning seemed a bit off.  So I changed that non-text box text to another Helvetica-style font and it did look better, but then when I set it back to Arial, it was garbled too.

Non-text box Arial Regular text when file is first opened. Kerning after a lowercase t looks a bit odd.

Set it to another font, then back to Arial Regular and this is what happens.

So do I have a bad Arial Regular on this computer?  If so, why don't other documents show this problem.  And, most important, how do I fix it?

Thanks in advance, and... HELP!