I've noticed an issue between 1.17.41, and 1.18.0. 

I've tried to upload a world (with addons) to my realm multiple times, but each time it doesn't work (view pictures). 

To use some of the addons I'm using, i have to use experimental gameplay; however.. regardless of if i use experimental gameplay, the same outcome happens.

(I'd also like to note.. I've tried doing what the dev on this bug said: REALMS-474 multiple times, but it never worked. I waited at least 5 minutes each time, on two different realms, but it never worked)