Can't upload continuation of realm world into realms

Sometime in October of last year, I finished my free trial on Realms. Afterwards, I downloaded the realm world for myself to work on alone. Until recently, I have worked on the world exclusively on my own. When I renewed realms two days ago, I tried to upload my world onto the realm, but it keeps failing with "Upload Failed! (500)", every single time after failing to verify the world, in which it would do that for 10 minutes. I don't think the server outages are really to blame that much, because when I upload ANY OTHER WORLD, it works just fine without issue. Now please tell me what's going on, because I'm getting rather annoyed on all this stupidity.