Illustrator CC 3D Object To Vector Problem

Hello,i am new to this forum and i would like someone to help me if can.I have a problem with 3D Object To Vector conversion.I have followed some youtube tutorials and in their case the conversion looks great,but in my case it has some problems with white lines.I have followed this tutorial:https://www.youtube.com/watch?v=rvgFN59-XAM Watch on 3:59 after he created the 3D Text,then he Expands it,and then he cuts the Top Text Layer(The Letter,not the 3D effect) and unites them all to get rid of the lines(i had that problem before i knew that),and when he goes to Paste In Front,it fits perfectly,and when i try that it has white lines as if the Letter is smaller.Please anyone who knows if he can to help me to fix this problem fast if possible,because im working on a Logo Project.Thanks!