I believe I've figured it out.
Highlight the outline of the band, richt-click properties, then select protection. Uncheck the Height selection box. Click ok.
Select Window>Show ShapeSheet. The first grid should be Shape Transform and the Height value will have a GUARD() function. Remove this wrapper. For example, change =GUARD(Sheet.62!Width*1) to =Sheet.62!Width*1.
Click the blue checkmark on the menu bar to accept the change.
You should now be able to change the height of the Functional Band.