Yes, the problem was you have used %blank% instead of %BLANK%. We have changed the shortcode in one question type and it is working fine. Sorry for replying late, but we are dealing with multiple requests at the moment hence the delay.
I understand your team must be very busy at the moment with the increased demand for QSM, which I presume is resulting from so many classes around the world shifting to online study and online tests and exams.
Thank you for your efforts. You may close this ticket off as resolved now.