Uploading a custom world to Realms leads to "This archives contains unclosed entires" error message.

I downloaded a map from Planet Minecraft, https://www.planetminecraft.com/project/drehmal-v2-prim-rdial-12k-x-12k-survival-adventure-map/ , and it works fine on singleplayer, but when I try to upload it to realms I get the error message "This archives contains unclosed entires". I have found bug reports bout this issue from a while back, but they were both unresolved and had no real solution. In case the file was corrupt I redownloaded it three times, and each time it didn't work. 

The world is 3 Giga bites and contains many command blocks. I don't know what to do.