Can you give us a bit more info.
Are you using report level columns?
Is each section a seperate report band?
If two tables elements are contained within a single band, have you tried setting the band stretch type to Container bottom?
Variable-Height Text Fields
Because text fields have dynamic content, most of the time you can’t anticipate the exact
amount of space to provide for them. If the space you reserve for your text fields is not
sufficient, the text content is truncated so that it fits into the available area.
This scenario is not always acceptable, so you can let the reporting engine calculate the
amount of space required to display the entire content of the text field at runtime, and
automatically adjust the size of the report element.
To do this, set isStretchWithOverflow to true for the particular text field elements
you are interested in. By doing this, you’ll ensure that if the specified height for the text
field is not sufficient, it will automatically be increased (never decreased) in order to be
able to display the entire text content.
When text fields are affected by this stretch mechanism, the entire report section to
which they belong is also stretched.
If they are Text elements you may want to check Detaisl overflow and stretch with overflow.
This is a good example of when working with text grid layout behavior: