Dynamics

I am now transcribing a piano sheet and there are going to be multiple parts played simultaneously. The parts appears one by one in order, and, to make the theme not to be overshadowed by other parts, I set Piano dynamics at other parts.

However, when I test the score I made, there is a segment that a part doesn't play in p (Piano dynamic), and after it, the volume is back to normal. I don't know what happened, any ideas?