It is due to the Auto Advance being toggled on when the survey is in Classic mode(single page). Please toggle off the Auto Advance option and click on save&apply button to get this resolved.
Refer screenshot for your reference - https://app.screencast.com/EHHZ0oAV6N8KWRefer help file - Auto Advance
Or the second solution to this is that you can change the survey layout to Focus mode
Can I use the back button in the classic design when page breaks are used?