Upload Failed! (This archives contains unclosed entires.)

I'm trying to upload a world to my realm and I keep getting this message. It won't even hit 0%, it will say "preparing your world" then it'll give me this message immediately. I've optimized the world and created a backup and tried uploading and keep getting the message. 

The world might be a bit heavy, It's a "minigame" map so it has a lot of command blocks as well as 20 (Yes, twenty) datapacks (loot table randomizers). What do I do? Is the file too big for realms to upload? It's been able to upload before, I've transferred this world many times from realms to singleplayer worlds frequently, as to keep a saved copy, and to edit the world with help of some of my friends.