Some frames of my render have pixelated distortions

I am using the newest version of After Effects cc

i am rendering out a 20 second 4K video. The video file I'm starting with looks perfect, it's something I rendered out of Blender. There is a lot of stuff going on in this render visually. When I put it into after effects, I overlay my signature and send the composition to Adobe media encoder.

in Adobe media encoder I chose h.264 and started with the 4K YouTube preset. Then I make sure the frame rate (24) matches my original video. I also select render at maximum but depth and render at maximum quality. I select high 6.2, and VBR 2 pass with a maximum bit rates of 90 and 110. 

ive also played around with all these setting trying significantly higher bit rates, VBR 1 pass, high unlimited instead of 6.2 and basically every setting I could think to change. My goal is to upload this video to YouTube. 

any tips on what I should be doing differently? My computer is rendering something at the moment but once it's finished I'll update this with a picture of the distortion and a picture of the settings I'm using