This issue usually occurs when the wireframe has extra components in the page that are not clearly visible to the user. For example an empty text component, or a rectangle component with no border ...
Here is an example screenshot with that issue :
In the editor, if you do select all, you can find there is an empty component as shown below:
How to fix this issue?
- Do a select all in the page
- Navigate to that part of the page and by clicking try to select the invisible component
- Delete or modify the invisible component from the page
- Now save and export the wireframe again