Exporting a word on a realms not working for iOS

Hello me and my friend mad a realm we successfully made one but when we try to export a world that we were playing on for a long time it was not working and we kept getting the same error: errors fails to upload. We try to export a small new world and it work fine but for some reason not our main one we try everything we could fiends on Reddit but nothing work is there a fix? Oh and btw the makers of the realms is playing on a iPhone (IOS)thank you