Crystal is never wrong about these things. She does exactly what you tell her ( which is not always what you think you did) . ......and that includes adding any blank space at the bottom of the page that you told her to put after the last field.
check your design and move the section line so that touches the bottom of the last field. and be sure to do the same in the page footer section.
If that doesn't work send a screen shot of the report in design mode so we can see what you are telling Crystal.