As mentioned in my previous answer the array size by default is 10.
It means, by default and without further action on your part, it can only contain up to 10 elements.
So when you try to put question 11 in the array, there is simply no room for it.
The fix is very simple, in LoadQuestionsFromString, add a blank sub-event before the "each question" loop.
Have this blank sub-event have the action QuestionsArray: Set size to (number_of_questions, 1, 1) and your array will fit the actual number of questions you are trying to put in.