Retry quiz not scoring correctly

I've recently moved up to Storyline 3 but am having trouble with the results of the quiz. 

We allow 3 attempts at the quiz and only retry the questions that were answered incorrectly. However results are only counting the reattempted correct questions. 

For example:

1. On first attempt I get 2 out of 4 correct answers, so result score is 50%

2. I retry incorrect answers and  I get 1 more correct answer but the result score is showing 25% not 75% (only counting the 1 correct answer I got on the 2nd attempt).

All of the triggers are correct and I have done this successfully in Storyline 2 lots of times.  Is there a variable or something else I can use to fix this?