Some student can't answer fill in the blank questions on Safari

During a Quiz last week, several student reported having difficulty answering questions in a Quiz. It seems to happen on Safari only, with the type of question "Fill in the blank".

When there is several blanks to fill, the system doesn't let the user fill the fields past the first one. The cursor keeps jumping back to the first field.

However, the students finally managed to answers the questions with lots of trying.