Engine thrust not straight in space

[RickyOri]

I built a probe where apparently solid state rockets do not work properly, in my pictures you can see two different probes, they are thrusted by the same engine from BDB, the "Vessel Viewer" (VV)  display shows that thrust is not aligned with center of mass even if the editor shows the opposite. The result is that in space, one probe rotates because of the bad thrust, the other one is fine (mistery goo one) even if VV displays the same thrust error.

So my questions are

1) Why isn't the engine's thrust straight aligned with the Center of Mass?

2) Why does it influences only one probe?

I'm using this engine: HLR-2911 "Vicenza-11" Solid State Thruster

images: http://imgur.com/a/oBwkpP7