Hello Fakhriyya,
I don't think this is fundamentally impossible. Another source shouldn't change the fields - Soft sources
Multiple sources could however change how the normalization works. I imagine that you are comparing Transmission results? Perhaps you could experiement with the different normlization states?
Also it could be possible that the simulation settings changed with this new source. Maybe it is using global source settings, and the global settings are different in this simulation?
If you have a bigger simulation you should check the the simulation time is sufficient, or the results can be different. This is 3D FDTD correct?
You are navigating away from the AIS Discovery experience