it's all just a bit over-compressed with the drop, it sounds like you've got a compressor on the master? & the vocal chops are way louder than your bass so it creates a weird pumping effect due to the attack/release not being set right. with a master compressor you want a short attack with a medium/long release, it should be subtle because remember it's working on everything!

also, the build/break before the drop is clipping slightly. make sure your meters aren't going into the red, instead of turning things up when you want them louder turn everything else down, you can bring it all back up at the end & make it all even louder without having it clip.