Covering up Answer Choices in Multiple Choice Question

After watching a demo on using an animated timer in Quizmaker, I am trying to incorporate this into a multiple choice question.  As one of the examples showed,  after the time runs out, I would like to cover up the answer choices with a message box and have an additional radio button appear in sync with the message box on the timeline.   I am using images to overlay the radio buttons for each answer option and I have sent the images to the back so that the radio buttons appear on top of the image. I imported the image of the message box and sent the image to the front.  The problem that I am having is that when I preview the question, sometimes it appears as I want it to, but sometimes the radio buttons that overlay the images do not appear and sometimes the radio button that I have synced with the message box appears before the set timing.  I'm not quite sure what I am doing wrong.  Any assistance would be greatly appreciated!