页面未完全使用

Question

我在我的文档（书籍类，默认为 \flushbottom）中发现并非所有页面都均匀拉伸到底部。在某些时候，下一页开始新的部分，之前的文本并不完全在底部结束，空白比应有的要多。有趣的是，如果我添加一行来拉伸内容，文本反而会移动到下一页。

有人知道问题可能出在哪里吗？看起来很奇怪。

\documentclass[12pt,twoside, openany]{book}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc} % Output font encoding for international characters
\usepackage[greek,english]{babel}
\usepackage{indentfirst} % Identation after chapter header
\usepackage{graphicx}
\graphicspath{{images/} }
\usepackage[labelfont={bf},
        %belowskip=-10pt,
           %aboveskip=0pt
        singlelinecheck=false
       ]{caption}                           
\usepackage{romannum}
\usepackage[toc,page]{appendix}
\usepackage{tabu}
\usepackage{xltabular}
\usepackage{booktabs,tabularx}
\usepackage{pgfplots}
\usepackage{boldline}
\usepackage{epstopdf}
\usepackage{multirow}
\usepackage{amsmath}
\usepackage{bm}
\usepackage{enumitem}
\usepackage{float}
\usepackage{wrapfig}
\usepackage{subfigure}
\usepackage{xcolor}
\usepackage{array}
\newcolumntype{P}[1]{>{\centering\arraybackslash}p{#1}}
\usepackage{comment}
\usepackage{textgreek}
\usepackage{parskip}
\setlength{\parskip}{\baselineskip}

\usepackage{url}
\urlstyle{same}
\usepackage[backend=biber,natbib=true,sorting=none,isbn=false,eprint=false,
doi=false,style=ieee,dashed=false,citestyle=numeric-comp]{biblatex}
\AtEveryBibitem{\clearfield{number}}
\addbibresource{Reference.bib}
\usepackage[intoc]{nomencl} % List of symbols
\usepackage{makeidx}
\makenomenclature
\renewcommand{\nomname}{List of Abbreviations}

\usepackage{setspace}
\usepackage{titlesec}
\titlespacing*{\section} % Spacing before/after (sub-) section titles
{0pt}{16pt plus 2pt minus 2pt}{18pt plus 2pt minus 2pt}
\titlespacing*{\subsection}
{0pt}{12pt plus 2pt minus 2pt}{10pt plus 2pt minus 2pt}
\setcounter{secnumdepth}{4}
\setcounter{tocdepth}{4}
\titleformat{\chapter}[hang]{\Huge\bfseries}{\thechapter{. }}{0pt} 
{\Huge\bfseries} % Title without "Chapter" but Nr. in front

\usepackage{amsmath}
\usepackage{geometry}


\usepackage{siunitx}
\usepackage[acronym,toc]{glossaries}              % use glossaries-package


\setlength{\glsdescwidth}{15cm}

\newglossary[slg]{symbolslist}{syi}{syg}{List of Symbols} % create add. symbolslist


\glsaddkey{unit}{\glsentrytext{\glslabel}}{\glsentryunit}{\GLsentryunit}{\glsunit}{\Glsunit}{\GLSunit}

\makeglossaries                                   % activate glossaries-package


\renewcommand*{\glossaryheader}{%  Change the table header
%\bfseries Sign & \bfseries Description & \bfseries Unit \\
%\hline
\endhead}
\renewcommand*{\glossentry}[2]{%  Change the displayed items
\glstarget{##1}{\glossentryname{##1}} %
& \glossentrydesc{##1}% Description
& \glsunit{##1}  \tabularnewline
 }
 }



\geometry{
paper=a4paper, % Change to letterpaper for US letter
inner=2.5cm, % Inner margin
outer=2.5cm, % Outer margin
bindingoffset=.5cm, % Binding offset
top=1.5cm, % Top margin
bottom=1.5cm, % Bottom margin
headheight=15pt 
}

\usepackage{fancyhdr}
\pagestyle{fancy}
\fancyhf{}
\fancyhead[LE,RO]{}
\fancyhead[RE,LO]{\rightmark}
\fancyfoot[RE,LO]{}
\fancyfoot[CE,CO]{\thepage}
\renewcommand{\headrulewidth}{0.4pt}
\renewcommand{\footrulewidth}{0.4pt}
%\setlength{\headsep}{0.4 cm} % Spacing between header and textblock below
\setlength{\footskip}{15pt}
\usepackage[bottom]{footmisc}
\fancyheadoffset{0pt}
\fancyfootoffset{0pt}
%\geometry{headheight=29.54742pt}
%\setlength{\headheight}{30pt}

%\setlength{\footnotesep}{0.5 cm}