[NTG-context] Strange math error (bug ??)

[WN]

Hello,

The following is quit strange, in the first formula the [{Q}, {R} ] on the
left hand side of the \rightarrow is not processed but on the right hand 
side of
the \rightarrow it is processed (?)

\starttext
The left side with $[Q,R]$ does not show, but the
right side with $[Q,R]$ does show, what is happening here ???
\startformula
[ {Q} , {R} ] \rightarrow \frac{1}{i \hslash} [ {Q} , {R} ]
\stopformula
\stoptext

Kind regards
Wim