cmi.suspend_data is indeed the field in the LMS where all values are saved that are “retained between sessions”. In Scorm 1.2 the field is limited to 4096 characters (for the whole course, not per question). As you can see in your screenshot a lot of space is already used for the page tracking.
By the way: The variable of a dnd question with 12 items is 53 characters long, while the variable of a multiple choice question is as long as all selected option texts so it can very easily be much longer.
But all values are stored in the same field, so it is not a problem with this individual question, it is just the one that usually exceeds the limit. But it may be the next, if your answers to the previous questions happen to be very short, e.g. if you select only 1 option for each mc question.