Oscillating pulse

Hello everybody:
I try to use the “Fimod” model to discuss the fiscal policy of China.I modify the model into two-country lineared model,but I am stuck with the problem of oscillating pulse.These are the pictures I get ,I don’t known how to remend my dynare code to get better result.Thank you very much, useless to say any help would be very much appreciated.
Dynare code.txt (14.1 KB)

Most of the time, this is a timing problem.