Wie konfiguriere ich eine Mindmap in Tikzposter? Die Figur in der Mitte wird nicht richtig angezeigt

Wie konfiguriere ich eine Mindmap in Tikzposter? Die Figur in der Mitte wird nicht richtig angezeigt

Das Poster

\documentclass[25pt, a0paper, portrait]{tikzposter}  
\usepackage[utf8]{inputenc}  
 \title{Tikz Poster Example}  
\author{ShareLaTeX Team}  
\date{\today}  
\institute{ShareLaTeX Institute}  
\usepackage{blindtext}  
\usepackage{comment}  
\usepackage{tikz}  
\usetikzlibrary{mindmap}  
\usepackage{metalogo}  
\usepackage{dtklogos}  
\usetheme{Desert}   
\begin{document}  
\maketitle  
\block{~}  
{  
    \blindtext  
}  
\begin{columns}  
    \column{0.5}  
    \block{More text}  
{\begin{tikzpicture}  
  \path [  
    mindmap,  
    text = white, align=flush center,  
    level 1 concept/.append style =  
      {font=\large\bfseries, level distance = 4.5cm, sibling angle=90},  
    level 2 concept/.append style =  
      {font=\normalsize\bfseries, level distance = 3.3cm, sibling angle=50},  
    level 3 concept/.append style =  
      {font=\small\bfseries, level distance = 3.5cm, sibling angle=75},  
    tex/.style     = {concept, ball color=black,  
      font=\huge\bfseries},  
    engines/.style = {concept, ball color=green!50!black},  
    formats/.style = {concept, ball color=blue!50!black},  
    systems/.style = {concept, ball color=red!80!black},  
    editors/.style = {concept, ball color=orange!90!black}  
  ]  
  node [tex] {Samples} [clockwise from=0]  
    child[concept color=green!50!black, nodes={engines}] {  
      node [circle,draw,minimum size=6em,text width=7em]{\Large\bfseries  {Mixtures}}[clockwise from=0]  
        child { node [circle,draw,minimum size=6em,text width=5em]  {\large\bfseries{Series 1}}[clockwise from=131]  
                child { node[circle,draw,minimum size=7em,text   width=7em] {\large\bfseries{DNA Conc.}} }  
                child { node[circle,draw,minimum size=7em,text width=8em] {\large\bfseries{Degradation}}}  
                child { node[circle,draw,minimum size=7em,text width=7em] {\large\bfseries{Sensitivity}}}}  
        child { node [circle,draw,minimum size=6em,text width=5em]  {\large\bfseries{Series 2}}[clockwise from=340]  
                child { node[circle,draw,minimum size=6em,text width=8em] {\large\bfseries{Proportions}} }  
                child { node[circle,draw,minimum size=6em,text width=8em] {\large\bfseries{No. of Contributors}} }  
                child { node[circle,draw,minimum size=5em,text width=7em] {\large\bfseries{Shared Alleles}} } }  
}
    child [concept color=blue, nodes={formats}] {  
      node {Case Types} [clockwise from=270]  
        child { node[circle,draw,minimum size=6em,text width=6em]   {\large\bfseries{40 Mixtures}} }}  
    child [concept color=red, nodes={systems}] {  
      node [circle,draw,minimum size=6em,text width=6em]{\Large\bfseries{Single source}} [clockwise from=240]  
    child { node [circle,draw,minimum size=6em,text width=5em]  {\large\bfseries{5 Samples}}[clockwise from=180]  
    child { node[circle,draw,minimum size=7em,text width=7em]   {\large\bfseries{LR Check}} }}  
    child { node [circle,draw,minimum size=6em,text width=5em]  {\large\bfseries{7 Samples}}[clockwise from=180]  
    child { node[circle,draw,minimum size=7em,text width=7em]   {\large\bfseries{DNA Conc.}} }}  
        child { node [circle,draw,minimum size=6em,text width=5em]  {\large\bfseries{7 Samples}} [clockwise from=180]  
          child { node[circle,draw,minimum size=7em,text width=7em]   {\large\bfseries{Saturation}} }}  
        child { node[circle,draw,minimum size=6em,text width=6em]  {\Large\bfseries{94 Samples}} [clockwise from=135]  
          child { node[circle,draw,minimum size=6em,text width=5em]   {\large\bfseries{Stutter Ratio}} }  
child { node[circle,draw,minimum size=6em,text width=6em] {\large\bfseries{Variances}} }}}  
    child [concept color=orange, nodes={editors}] {  
      node {STRmix} };  
\end{tikzpicture}}  

    \column{0.5}
    \block{Something else}{Here, \blindtext \vspace{4cm}}
    \note[
        targetoffsetx=-9cm, 
        targetoffsety=-6.5cm, 
        width=0.4\linewidth  
        ]  
        {e-mail \texttt{[email protected]}}  
\end{columns}  
\begin{columns}  
    \column{0.5}  
    \block{A figure}  
    {   
            {\blindtext}       
    }  
    \column{0.5}  
    \block{Description of the figure}{\blindtext}  
\end{columns}  
\end{document}  

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