Edit: I didn't notice the one problem per report rule so I made another one to fix this problem.

Me and a few other people have been making an adventure map and we had to remove a certain area of our map with the /fill command (/fill ~-10 ~-20 ~-10 ~10 ~ ~10 air) because when we walked into that area we dropped from 60+ fps to 1fps before the server/map would kick us. We couldn't look in the direction of that area for a while because it would either drop our frames to lower than 20 or so low that we couldn't move and would have to teleport each other out of the area. using the /tp command.  This started a few weeks ago.

Tonight, after fixing the other problem on our map (problem MC-215412 ) we still have bad framerate drops over that area to the point where Minecraft stops responding completely. I have attached images from both me and my friend's views plus a debug report when it happened just now.

Any help is wanted at all.