It seems that the header is limited to three lines only. See the attached screenshot.
To reproduce:
\chapter{ Lorem ipsum dolor sit amet, consectetur adipiscing elit. Phasellus laoreet odio interdum ex elementum commodo. }
Lorem ipsum dolor sit amet, consectetur adipiscing elit. Phasellus laoreet odio interdum ex elementum commodo. Integer quis arcu feugiat, pharetra turpis vestibulum, luctus sem. Nullam et vehicula augue, non varius est.
It seems that the header is limited to three lines only. See the attached screenshot. To reproduce: