Breaks/interruptions in matrix lines occur when using 'fleqn'

I need to build a matrix. Some of the expressions inside and outside the matrix are long due to which breaks/interruptions occur in the right side of the matrix lines. The image is attached. When the matrix size is reduced, the breaks disappear. How can I remove the breaks with the existing matrix size? The MWC is given here

\documentclass[journal]{IEEEtran}
\usepackage{amsmath,blkarray}
\usepackage{rotating}
\usepackage{lscape,bm}
%\usepackage{showframe}
\usepackage{pdfpages}
\usepackage{amsmath}
\usepackage{nccmath}
\usepackage[paper=portrait,pagesize]{typearea}
\begin{document}
    \onecolumn
    \KOMAoptions{paper=landscape,pagesize}
    \recalctypearea
    %   \begin{landscape}
        %\begin{sidewaystable}
        \noindent
        %\begin{center}
        %\textbf{\underline{{\large Supplementary Material for Review}}} 
        %\end{center}
        %\smallskip
        %We can derive the transition rate matrix for the proposed model as follows
        \begin{fleqn}
            \[
            \mathbf{P} = 
            \begin{blockarray}{c@{\hspace{1pt}}ccccc@{\hspace{3pt}}}
                & 1   & 2   & 3 & \cdots & 20 \\
                & (p_n , s_n, p_r, s_r, f, c) & (p_n+1, s_n, p_r, s_r, f, c)  &(p_n, s_n+1, p_r, s_r, f, c) & \cdots & (p_n, s_n, p_r, s_r, f-1, c)\\
                \begin{block}{r@{\hspace{1pt}}|@{\hspace{1pt}}
                        |@{\hspace{1pt}}ccccc@{\hspace{1pt}}|@{\hspace{1pt}}|}
                    1 ~~~~~~~~~~~~~\\ (p_n , s_n, p_r, s_r, f, c)   & -(\lambda_P+\lambda_S+\cdots +f \mu_R) & \lambda_P & \lambda_S & \cdots & f \mu_R \\
                    2 ~~~~~~~~~~~~~ \\ (p_n+1, s_n, p_r, s_r, f, c) & p_n\mu_P & -(p_n\mu_P+0+\cdots + 0) & 0 & \cdots & 0\\
                    3 ~~~~~~~~~~~~~\\ (p_n, s_n+1, p_r, s_r, f, c) & s_n\mu_S   & 0   & -(s_n\mu_S + 0 + \cdots + 0)   & \cdots & 0\\
                    \vdots ~ ~ ~~~~~~~~~~~~ & \vdots  & \vdots   & \vdots   & \vdots & \vdots\\
                    20 ~~~~~~~~~~~~~\\ (p_n, s_n, p_r, s_r, f-1, c) & (\Theta-\Omega(\bm{x}))\;\lambda_F  & 0   & 0   & \cdots  & -((\Theta-\Omega(\bm{x}))\;\lambda_F + 0 + 0 + \cdots + 0) \\
                \end{block}
            \end{blockarray} 
            \]
        \end{fleqn}
    \end{document}