Assessment does not score on 2nd try

Hi, I have 100 questions assessment with 90 minutes timer. I'm getting inconsistence result when I test this on Sumtotal LMS. Here is the problem:

First try, I answer 15 questions correctly and let the timer run out of time.

Result: I get 15% on the result page and count rest of the questions incorrect. This works as designed.

Second try, I re-register for the course again in the Sumtotal and answer all 100 questions correctly

Result: On the result page, sometimes I get 100% and other times I get 0% and it reports as Failed in the LMS.

Question: Do anyone know why it would be inconsistent in the 2nd try? Does Lectora keep any data from previous attempt in the cookie?

Any help would be appriciated...thanks