[XeTeX] Strange issue with tanwin, arabxetex

[Nathan Camillo Sidoli]

Hello Everyone,

Over the weekend I updated both my system (to Mac OS 10.10), and TeXlive 
(to 2015).

Now I have an issue with tanwin for indefinite accusatives in ArabXeTeX. 
Here is a minimal example:


\usepackage[novoc,fdf2noalif]{arabxetex}
%\oldtanwin
\newfontfamily\arabicfont[Script=Arabic,Scale=1.4]{Amiri}% Traditional 
Arabic, Amiri
\newcommand{\A}{\textarabic}

\begin{document}

\A{_h.t"aN} $\quad$ \A{m_tl_t"aN}

\bigskip

\A{خطًا}  $\quad$ \A{مثلثًا}

\A{%
إذا أضيف إلى خط مستقيم معلوم سطح متوازي الأضلاع معلوم
ينقص عن تمامه سطحًا متوازي الأضلاع معلوم الصورة، فإّنأضلاع السطح الباقي معلومة
}

\end{document}

When I compile this document, a tanwin in the unicode input (etc., خطًا) 
is stripped out in the output. (If I just use polyglossia this does not 
happen, but for various reasons I am committed to also using ArabXeTeX.)


This behavior did not happen before the upgrade - that is, the tanwin 
appeared as in the input. I have tried switching back to my TeXlive 2014 
distribution, but now this behavior is also happening when I compile 
with that distribution as well. That is, it seems to have been produced 
by updating my OS. I'm not sure what could be causing this behavior and 
any suggestions would be welcome.

Best,

Nathan