This may be because of how your form’s Logic is set up.
Double-check any rules you’ve created to confirm that you aren’t accidentally skipping questions, and use your Logic Map as a handy reference to make sure your respondents are being sent down the right question paths.
Remember, logic works in a flowchart format. Every flowchart has a Start and an End (your first and last fields). So you shouldn't add logic to your first and last questions.
If you want to add logic to your last question, you can either add a section field after it or add a field after it that never shows up in your logic path!