Check your Lesson settings. Sounds like you have max attempts of 1. See The Maximum Number of Attempts by a Student in MoodleDocs. This feature prevents a student from going into an endless loop. If you set it to 3, the student would have 3 attempts at getting the question right before automatically being sent to the next page. This feature also helps when the teacher forgets to set any of the jumps to go to another page
Hope this helps. Common question, I will make sure it is added to the Lesson FAQs .
Chris