Leandro,
I have to agree with the folks recommending the ground plane. I run Legacy in S gauge. I was running a pair of diesels, Legacy U-33s, there were places on my layout where I was operating them as a consist or lash-up if you prefer, and one of the locomotives would lose the signal and the other engine would continue to pull. I did add the ground plane and that solved the problem. I did at a later date also add the signal booster designed by Dale and John for added insurance.
Ray