Error combining PDFs with DocuSign Signature

We are running on Windows 7 and have recreated this error with Acrobat XI Standard, Acrobat DC and Acrobat 2017.

When combing a large number of 2 page PDFs with DocuSign signatures (each 397 KB).  The 129th PDF forward will be flagged with the error "Acrobat does not support the conversion of one or more of your files to PDF. Please remove the files from the list."  We can combine 200 PDF's without DocuSign Signatures and there is no issue. We can combine those same 200 PDFs with 128 DocuSign PDFs and there is no issue until we get to 129. 129 is the magic number.

If I break the number of PDFs into small batches and then combine those PDFs the process will work but only if I exit Adobe before the total number of documents of PDFs opened reaches 129.

For example, this workflow works:

1. Open Acrobat
2. Combine Files: Open and Combine 60 PDFS into Binder1.pdf
3. Close Acrobat
4. Open Acrobat
5. Combine Files: Open and Combine 70 PDFS into Binder2.pdf
6. Close Acrobat
7. Open Acrobat
8. Combine Files: Open and Combine Binder1 and Binder2.pdf

This workflow does not work:

1. Open Acrobat
2. Combine Files: Open and Combine 60 PDFS into Binder1.pdf
3. Close Binder1
4. Open 70 PDFs

This will generate the error beginning with the 69 file of the second batch or the 129th file opened while Acrobat is in memory.

Thank you for any sight.