How do I get consistent margins in dramatist?

Question

The code:

\documentclass[a5paper,11pt]{memoir}    
\usepackage{dramatist,etoolbox,enumitem}
\usepackage[latin]{babel}
\pagestyle{empty}
\makeatletter
\renewenvironment{drama}
  {\if@lnpa
   \PackageWarning{dramatist}{\lnpwarning{a}}
   \fi
   \if@lnps
   \PackageWarning{dramatist}{\lnpwarning{s}}
   \fi
   \begin{itemize}[labelwidth=\speakswidth,leftmargin=!]} 
  {\end{itemize}}
\patchcmd{\speaker}{\item[#1\speaksdel]}{\item[\speaksfont#1]}{}{}
\patchcmd{\@character}{\item[#1\speaksdel]}{\item[\speaksfont#1]}{}{}
\makeatother
\begin{document}

\Character[Carl - a person]{Carl}{carl}  % define characters
\Character[Riva - a person]{Riva}{riva}
\settowidth{\speakswidth}{\speaksfont{Frederico}\speaksdel\hspace{\speechskip}}

\StageDir{
    \begin{center} Chef
     \end{center}
}

\begin{drama}
\rivaspeaks Carl. Carl. We're staying with the same menu, right?
\carlspeaks I have something really good planned for tonight. I'm gonna let you... It's not sweetbreads. You're gonna be able to taste it.
\rivaspeaks That may be true. But we have the most reservations on a work night since we opened. You realise that?
\carlspeaks I know. I was on Twitter.
\rivaspeaks Yeah.
\carlspeaks I was promoting the restaurant. I was on Twitter.
\rivaspeaks What? Yeah, that's another thing. From now on, before you post anything online, I OK it. Alright?
\carlspeaks The whole reason everybody's here tonight is because I called out Ramsey Michel online and they're all coming to watch me stick it in his ass.
\rivaspeaks Yeah, and you're gonna twitter an apology for calling the most respected critic in Los Angeles an asshole.
\carlspeaks I'm not gonna fucking apologise.
\rivaspeaks What do you mean, you're not...
\carlspeaks You see what he wrote about me?
\rivaspeaks I don't give a fuck...
\carlspeaks He started it!
\rivaspeaks I don't care.
\rivaspeaks You're a cook. You're a chef. This is what you've been cooking for years, and it works. And either you cook the menu that our customers have come to ex...
\carlspeaks You want me to cook the same food?
\rivaspeaks The same exact...
\carlspeaks The same food that he ripped apart? The same guy who's coming tonight?
\rivaspeaks The restaurant isn't filled with critics! It's filled with people that've been eating your food for the last 10 years! So now, suddenly, you're gonna be an artist. Well, be an artist on your own time.
\carlspeaks Listen to me.
\rivaspeaks No sweetbreads!
\carlspeaks Listen!
\rivaspeaks No calves' brains.
\carlspeaks I'm not cooking sweetbreads! Listen to me. The kitchen is my domain. That was our deal.
\rivaspeaks I don't give a fuck what the deal was! The deal is now changed. Either you stay or you go. It's up to you. End of discussion.
\end{drama}

\end{document}

The output:

The text is off center on every other page. How do I center it? Thanks.