You can get these types of error-messages because OpenModelica checkModel does not check local balance of models. Consider for example:

model M

  Real x,y,d;

equation

  d = 0;

  x = time + y*d;

  x = sin(time);

end M;

checkModel will tell you this system is fine because it has 3 equations and 3 variables.

But if you try to simulate the model, the compiler tells you it cannot solve for y. (Or that it could not sort for x and y).

I would guess an optimization module transformed your model into something that looks like this and the sanity check caught it.

+d=optdaedump can be used to debug the optimizations when running omc from command-line.

Thank you
It help me