PDF-Optimizer doesn't work on interactive pdf

Hello.

In my Adobe Acrobat Pro 9 (on OSX 10.11.6) , the PDF Optimzier won't work on an interactive file containing both hyperlinks and cross references to pages (no anchors), albeit that file most certainly can be reduced (may hig res images). On first run, it claims it's flattening transparencies, and while claiming so, Activity Monitor shows the application as unresponsive with a high cpu load. Then it simply seizes working, saves no file, does nothing, but becomes responsive with very low cpu load. Upon second attempt, it doesn't even start: Activity Monitor shows no activity at all, no invisible file (invisible files are visible in my finder) appears, Acrobat remains fully responsive, everything is just as if the PDF Optimizer command had never been given. I did try different settings (don't discard anything), different file names to save to, and checked the privileges on the files in question, restarted the app and the machine, no change.

However, PDF Optimizer still does work on non interactive files. So, is there any rule or reason for it not to work on interactive pdfs?

Thanks a lot.