Q: Weird chorus effect on vocal

Hey there,
I'm super fresh to MainStage 3. This Friday I play a GIG and I needed MainStage to help me with it... and I love it! It's so cool. I'm learning all the stuff quite easily, but this one is kind of hard to guess:

How do I fix that weird vocal effect (chorus like) on vocal? I'm running both, my vocal and instrument through MainStage, it is essential too me that it worked. It's kind of like there's two sources of vocal. I'm using Focusrite Liquid Safire 56, but I've muted the hardware monitoring in it, so there should be no problem... I don't use Logic as my DAW, so I guess there's something I could be skipping, as I'm new to this environment.

Let me know if you could help

Take care,
Michal