Combining pages from multiple ADA accessible PDF files brings back the accessibility issues

We have to submit a large 100 page packet to the board. This packet consists of multiple smaller (1-3 pages) files that were sent to me by various people within the company. They were all made ADA accessible in Word, PPT, Excel, etc. then converted to PDF and made accessible using Adobe Acrobat Pro DC. When I combine all of the accessible files to make up one packet all of the accessibility issues reappear. Does anyone know how to solve this problem?

Combining all of them into a large packet and then checking for accessibility is not an option as the files come from multiple people and no one has the time to make all 100 pages accessible on their own.