11.4.0
I find OCR can't process some PDFs, getting stuck on the first page (sometimes the last). However if I use the PDF to images and then images to PDF I can rebuild the PDF, and it then OCRs. I've just checked and using the Convert to... and choosing PDF also effectively makes it OCR'able.
It may be you may want to think about the logic of what's happening but also something to detect OCR getting stuck and recommending or offering a rebuild.
Cheers, David