It looks like windows 10 update put on version 1809 about when I think this started happening. I have one computer that was updated later that is still within 10 days and I can take that off, which I'm going to try.
1809 had some...issues. In my personal collection I had one PC which stopped being able to initiate a Remote Desktop connection. Three others still worked fine with the exact same updates installed. No amount of troubleshooting or Services tweaking could shed light on it. It was then mysteriously fixed in a Patch Tuesday update about two or three weeks later.
The only thing I've encountered with Adobe Acrobat specifically is that the distiller (in some versions, anyway) defaults to 1200dpi rendering, which reacts badly with older Windows programs that don't fully subordinate themselves to the System Print Dialogue. The result can be huge or corrupted PDFs that can also choke print queues. But that's probably not your issue here, and wouldn't explain the JPG image behavior regardless.