xcolors cellcolor 叠加 tikz 背景

Question

我正在使用mdframed选项tikz来定义我自己的环境。不幸的是，如果我使用带有命令的tabularx环境，它会覆盖我的框的标题。xcolor\cellcolor

这是一个最小的工作示例：

\documentclass[a4paper,10pt,DIV=1]{scrreprt}

\usepackage{multirow,tabularx}
\usepackage[table]{xcolor}
\usepackage[framemethod=tikz]{mdframed}

\mdfdefinestyle{mystyle}{%
    linecolor=black,
    linewidth=0.5pt,
    topline=true,
    innerleftmargin=0pt,
    innerrightmargin=0pt,
    innertopmargin=0pt,
    innerbottommargin=0pt,
    frametitleaboveskip=1.2\dimexpr-\ht\strutbox\relax,
}

\makeatletter
\def\field{\cellcolor{gray!25}~}%
\makeatother

\newenvironment{ProtocolBox}[1][]{%
    \mdfsetup{%
        style = mystyle,
        frametitlealignment={\hspace*{0.01\linewidth}\vspace{-1.63em}},
        frametitle={%
                \tikz{[
                    baseline=(current bounding box.east),
                    outer sep=0pt
                ]
                \node[
                    draw = white,
                    line width = 1pt,
                    text = black,
                    anchor=east,rectangle,
                    fill=white,
                ]
                {\strut #1};
            }
        }
    }
    \begin{mdframed}[userdefinedwidth=\linewidth]\relax%
}{\end{mdframed}}

\begin{document}

    \begin{ProtocolBox}[Header]
        \begin{tabularx}{\linewidth}{X}
             \vspace{0.1em}\field The Background of the cell is overlaying the background of the box header
        \end{tabularx}
    \end{ProtocolBox}

\end{document}

你知道我该如何定义图层的“顺序”，以便标题背景始终位于前面吗？

谢谢