Edited
I am very new to LaTeX and I have just compiled my thesis using twoside (it had been oneside previously). On a few random horizontal pages the Chapter header (which has been shortened using \chaptermark{}) is offset and runs off the side.
Here is some compilable code and the image I use is attached:
\documentclass[12pt,twoside]{book} %,PageStyleII,times,numbering,print,custombib \usepackage{geometry} % See geometry.pdf to learn the layout options. There are lots. \geometry{a4paper} % ... or a4paper or a5paper or ... \usepackage{floatrow} \usepackage{setspace} \usepackage{caption} \usepackage{subcaption} \usepackage{graphicx} \usepackage{lscape} %\usepackage{float} \usepackage{booktabs} \captionsetup[figure]{font={small}, skip=1pt, singlelinecheck=false} \captionsetup[subfigure]{font={small}, skip=1pt, singlelinecheck=false} \captionsetup{labelfont=bf} \captionsetup[table]{font={small}, skip=1pt, singlelinecheck=false} \raggedbottom \usepackage{lineno} \usepackage{mathtools} \usepackage[all]{nowidow} \usepackage{tocloft} \usepackage{xpatch} \usepackage{enumitem} %\usepackage{amssymb} \usepackage{cite} \usepackage{natbib} \renewcommand\bibname{References} \usepackage[nottoc]{tocbibind} \usepackage{appendix} \usepackage{chngcntr} \usepackage{longtable} \usepackage{color, colortbl} \definecolor{lightgray}{gray}{0.9} \floatsetup[table]{capposition=top} \usepackage{makecell} \begin{document} % ******************************** Main Matter ********************************* \mainmatter \chapter{Assessing the evidence for microenvironments in craters} \label{chap:micro} \chaptermark{Microenvironments in craters} %********************************** %5th Section ************************************** \section{The environment at Kaiser crater} Blah blah blah \subsection{Surface temperature} The blah blah blah \newpage blah blah \newpage \begin{landscape} \begin{figure}[H] \begin{center} \includegraphics[width=0.95\hsize]{Micro/windsx4_Kaiser_ls110.png} \caption{one page horizontal which plots ok.} \label{fig:ktsurf} \end{center} \end{figure} \newpage \begin{figure}[H] \begin{center} \begin{subfigure}{0.95\hsize} \subcaption{\bf SH mid-summer} \label{fig:ktsurf_110} \includegraphics[width=0.95\hsize]{Micro/windsx4_Kaiser_ls110.png} \end{subfigure} \caption{This plots chapter header offset.} \label{fig:ktsurf_winds} \end{center} \end{figure} \begin{figure}[H]\ContinuedFloat \begin{center} \begin{subfigure}{0.95\hsize} \subcaption{\bf SH late autumn} \label{fig:ktsurf_230} \includegraphics[width=0.95\hsize]{Micro/windsx4_Kaiser_ls110.png} \end{subfigure} \captionsetup{justification=centering} \caption[]{This plots OK} \end{center} \end{figure} \begin{figure}[H]\ContinuedFloat \begin{center} \begin{subfigure}{0.95\hsize} \subcaption{\bf SH early spring} \label{fig:ktsurf_350} \includegraphics[width=0.95\hsize]{Micro/windsx4_Kaiser_ls110.png} \end{subfigure} \captionsetup{justification=centering} \caption[]{This plots OK} \end{center} \end{figure} \end{landscape} \end{document} This only happens when the second horizontal page is on the right hand side / is an even page number. When I compiled it and the first horizontal page was on the right hand side, the rest was all fine.
Thanks 
