Wrong forecasts

Hello,
I have a problem. I get different forecasts for the same model and I do not know why. They only differ in the way, the consumption tax is introduced (mathematically, it is equivalent):

In model 1, I use the expression (e_c+t) in all equations.
In model 2, I use the expression t_c in all equations. t_c is later defined as e_c+t.

Model 1 (wrong forecasts):

[code]%----------------------------------------------------------------
% 1. Defining variables
%----------------------------------------------------------------

var w d k n y x c z t s;
varexo_det e_c;
varexo e;

parameters beta alpha delta phi rho;

%----------------------------------------------------------------
% 2. Calibration
%----------------------------------------------------------------

phi = 0.38;
beta = 0.99;
delta = 0.0175;
alpha = 0.319;
rho = 0.95;

%----------------------------------------------------------------
% 3. Model
%----------------------------------------------------------------

model;
// Household
((1-alpha)/alpha)(c/(1-n)) = w/(1+e_c+t); /consumption-leisure tradeoff/
alpha
c^(-1)/(1+e_c+t) = beta*(alpha*(c(+1))^(-1)(1+d(+1)-delta))/(1+e_c(+1)+t(+1)); /Euler equation/
(1+e_c+t)c + x = s + nw + d
k(-1); /budget constraint/
k = k(-1)*(1-delta) + x; /capital accumulation/

// Firm
y = exp(z)*(k(-1)^phi)*n^(1-phi);
w = (1-phi)y/n;
d = phi
y/k(-1);

// Government
t = 0.2;
s = (e_c+t)*c; /*Tax revenues from consumption taxation are redistributed through transfers s */

// Shocks (not important)
z = rho*z(-1) + e;

end;

%----------------------------------------------------------------
% 4. Computation
%----------------------------------------------------------------

initval;
w = 3.09316;
d = 0.027601;
k = 16.6054;
n = 0.241758;
y = 1.20612;
x = 0.290595;
c = 0.915528;
z = 0;
t = 0.2;
s = 0.183106;
end;

shocks;
var e = 0;
var e_c;
periods 21:500;
values -0.01;
end;

stoch_simul(periods = 501, order = 1);
forecast;[/code]

Model 2 (right forecasts):

[code]%----------------------------------------------------------------
% 1. Defining variables
%----------------------------------------------------------------

var w d k n y x c z t s t_c;
varexo_det e_c;
varexo e;

parameters beta alpha delta phi rho;

%----------------------------------------------------------------
% 2. Calibration
%----------------------------------------------------------------

phi = 0.38;
beta = 0.99;
delta = 0.0175;
alpha = 0.319;
rho = 0.95;

%----------------------------------------------------------------
% 3. Model
%----------------------------------------------------------------

model;
// Household
((1-alpha)/alpha)(c/(1-n)) = w/(1+t_c); /consumption-leisure tradeoff/
alpha
c^(-1)/(1+t_c) = beta*(alpha*(c(+1))^(-1)(1+d(+1)-delta))/(1+t_c(+1)); /Euler equation/
(1+t_c)c + x = s + nw + d
k(-1); /budget constraint/
k = k(-1)*(1-delta) + x; /capital accumulation/

// Firm
y = exp(z)*(k(-1)^phi)*n^(1-phi);
w = (1-phi)y/n;
d = phi
y/k(-1);

// Government
t_c = t + e_c; /t_c is defined as in model 1/
t = 0.2;
s = t_c*c; /*Tax revenues from consumption taxation are redistributed through transfers s */

// Shocks (not important)
z = rho*z(-1) + e;

end;

%----------------------------------------------------------------
% 4. Computation
%----------------------------------------------------------------

initval;
w = 3.09316;
d = 0.027601;
k = 16.6054;
n = 0.241758;
y = 1.20612;
x = 0.290595;
c = 0.915528;
z = 0;
t = 0.2;
s = 0.183106;
end;

shocks;
var e = 0;
var e_c;
periods 21:500;
values -0.01;
end;