Microsoft Word 2013 (v15) Save Glitches On Older Documents

So my wife has been having this issue for a while now with her Toshiba laptop we got for her classes last year. What happens is that if she opens a document that's even slightly old (even her newest document, from about three weeks ago), the Save button in the top-left corner will open a Save As dialogue box instead of just saving the document. But this doesn't happen with the document that I just saved (which is an updated version of that document from a few weeks ago), and it's in the same folder. I don't know how old the document needs to be before this happens, but I find it strange that it happens specifically with older documents but not with newer documents.

So she's able to save as a new document via the resulting dialogue box, but if she tries to save to the same file name (updating), there's a second glitch that pops up.

If she tries to Save As with the same file name and update the file, it spits out the error "Word cannot complete the save due to a file permission error."

I've tried looking up fixes for these issues separately, but nothing has helped from the M$ forums or anywhere else that I've found separate solutions. Has anyone heard of these things happening together or how it might be fixed? This frustrates her quite a bit, ad she asked e to try and fix it for her, but I've had no luck thus far.

It's running Windows 10, if that helps at all.