Data of Opaque attempts disappear.

Dear all,

When i use the Opaque question engine(Moodle 1.9.9+) as student in a quiz, i can save, submit and review the result from the web service within Opaque question engine.(fig.1)

While, if i change my role to teacher to preview the quiz, only the score of the attempts are there, but all other things gone. (fig.2)

I find this problem may caused by the data in the folder 'moodledata\sessions' has been overridden by the teacher's action, but have no idea how to fix this.

Please advise how can i fix this. 

Many thanks.