Error in Quiz using Chrome "error player_DoJSCommand is undefined"

My LMS support folks (NetExam) are looking at an issue where users

1) Can't complete an already (previously passed) course using Chrome . When using Google Chrome, the finish button at the end of the quiz was not working; nothing happened if they clicked on it. 

 Can operate complete button in IE10 but a completion doesn't get logged see 2) below. 

2) NetExam did not update the user with the new completion date - only showed the original date (often more than a year ago) when that user 1st completed the course and quiz.

Their engineers  have found, using Google Chrome an error "error player_DoJSCommand is undefined".

 They asked me to check my SCORM files; since this applies to at least 7 different courses/quizzes, I cannot see how the SCORM files can all have suddenly failed or got corrupted !

 Anyhow they work ok for 1st time users, registering everything correctly.  

 I ran 1 of these courses at SCORM Cloud with no problems detected either.

 Netexam support's last communication to me says " If you can please recheck the scorm package file with the scorm developer."

 Any idea what the error message means ?

["error player_DoJSCommand is undefined"]

 I am stuck as to what to do next. 

Chris Muriel, Manchester, UK