Problem combining multiple jpegs into single PDF

Hello... I apologize for re-posting a problem, but my first attempt 3 days ago was flagged as spam, unflagged in the middle of the night, and then someone made a phishing attempt to get my account info. I have not come to the forums very often, but when I have I appreciate the help I've gotten. This time, however, has not been a good experience. But I really need help, so I'm asking again. 

Original post here for background.

Mac OS 10.12.6

Acrobat DC 19.021.20049

After several attempts at figuring it out for myself, I've discovered that I can only combine 15 jpeg files (4mb average) at a time to create a combined pdf document, and then combine the next 15, and the next, until all the files are combined (100 average). Then I have to combine the resulting 4, 5, or 6 PDFs into a single PDF.

So, it's not the jpeg files that are the problem... it's the process.

A month ago "Combine Files into a Single PDF" did not present this limitation, which is now adding significant time to this giant archive project. I tried PDF Portfolio, but that does not seem to include the tools I need to complete each issue (OCR, text editing, indexing, etc.).

What has changed and how can I get back to the workflow I had been previously using for the last 5 years that I've been working on this project?

Thank you in advance for any help you can offer.

Susan