Maya : Error with MargDatabase in c#



I have an issue when trying to parse arguments in my c#.
I have a command in c#, and I try to create the MargDataBase from the receive MArgList.

void doIt(MArgList args)

MArgDatabase data = null;
      data = new MArgDatabase(syntax, args);
catch (Exception e)
       MGlobal.displayError( $"Cannot Parse Args for the command, Abort!\n {e.Message}");

But it throws an internal failure exception and I cannot use it.

I am using .Net API, Windows 10, Maya 2017 Update 3

The command is called from Python.

What could cause this failure?

PS : it does not always fail…