So I was looking at my phone and I see three lines separating the antennas. so I was thinking why are the lines there in the first place. well there are there because each piece has a specific function and they put those black lines there so that the antennas wont touch and interrupt each function. so my theory is when you place your finger on the line you are somehow connecting the two pieces together with your finger as a conductor and that somehow interrupts the flow of something and it causes the signal to drop. I've done test where my finger almost touching the line and I dont have a signal issue only when I actually place my finger and connect the to metal pieces together then I have an issue.