When the piano plays the main melody it seems to change the song's energy too much. That melody is so sad, the rest of the song is groovin. For me the contrast makes the song hard to listen too, but I really like the energy of each alot. I really like your middle section.
You can find a way to blend them together, maybe by customizing the drums to emphasize beats in the melody, or maybe adding a bassline will tie everything in.