[stem] and [env.equation] have differences, [env.equation] seems to support less

[prudhomm]

Hi

[stem]
+++
+++

and

[env.equation]
--
--

don' t seem to support the same latex command and [env.equation] seems to support less latex than [stem]

[env.equation]
.Momentum conservation equation
--
\rho_{f} \left. \frac{\partial\mathbf{u}_f}{\partial t} \right|_\mathrm{x}
+ \rho_{f} \left( \boldsymbol{u}_{f} \cdot \nabla_{\mathrm{x}} \right) \boldsymbol{u}_{f}
- \nabla_{\mathrm{x}} \cdot \boldsymbol{\sigma}_{f} = \boldsymbol{f}^t_f , \quad \text{ in } \Omega^t_f \times \left[t_i,t_f \right]
--

[stem]
++++
\rho_{f} \left. \frac{\partial\mathbf{u}_f}{\partial t} \right|_\mathrm{x}
+ \rho_{f} \left( \boldsymbol{u}_{f} \cdot \nabla_{\mathrm{x}} \right) \boldsymbol{u}_{f}
- \nabla_{\mathrm{x}} \cdot \boldsymbol{\sigma}_{f} = \boldsymbol{f}^t_f , \quad \text{ in } \Omega^t_f \times \left[t_i,t_f \right]
++++

attached the rendered math, above with [env.equation] fails while there are no problem with [stem]

any idea ?