Adobe Reader "read out loud" stops before end of document

I have a persistent problem with Adobe Reader's "Read out loud" function on the free version of Adobe Reader.  When I select "read to end of document," it quits before reaching the end.  Always!

I have asked it numerous times to read out loud to the end of a 120-page screenplay -- not a heavy lift, since the total text volume is about 20,000 words.   The furthest it has ever reached is page 30; just now it died at the end of page 12.   I restart Adobe, reboot the computer, update to the latest Adobe Reader version, etc., etc. -- all useless!   This "read out loud" feature is broken and, for me at least, worthless.  Is Adobe trying to get me to  upgrade to a reader with a better "read out loud" function?   At the very least, it could flag the reason it quits!

My computer is an iMac running OS X El Capitan (OS 10.11.60, with 4 GB of memory.  My Adobe version is 11.0.18.