Why three phase two winding transformer is giving unbalanced currents at primary side when I am using a circuit breaker in the circuit?

 I need some help regarding the three phase two winding transformer in MATLAB Simulink. I have two cases of simulation which are given below

1: There is no circuit breaker in the circuit and transformer secondary side is open. I am getting balanced primary currents.

2: In second case I have introduced the circuit breaker (you can consider it as a switching) after some time but now the current are not balanced. Could you please explain it to me why is it? All conditions are same as in case 1. I am sending you the model please find the attached.

Note: in first case you can remove the circuit breaker or put it on from the start.