For everyone still struggling and subscribed to this issue: I WAS able to upload a world on Xbox. On my wired 200mbps internet it didn't work. On my 5Ghz Wi-Fi with the same speed it didn't work. But when I turned on my phone's hotspot (Pixel 5a, T-mobile) and used the slow mobile data, for some reason it worked perfectly. So if you haven't tried that, give it a shot.
For the record, for some reason my wired internet had ipv4 only, strict NAT, and no uPnP, but my Wi-Fi had ipv4 and ipv6, open NAT, all services operational. Don't know why but the point is I tried both of those, neither worked, but phone data for some reason did work.
Cannot upload an existing world to my realm. July 2022 on an Xbox One X with all the latest updates. I tried uploading it to a blank slot and replacing a world–neither worked. Got the blank "initializing upload" bar followed by the error.
Just happened to me on latest Bedrock on Xbox One X, 8/2/22. Took no damage from sword as expected but was lit on fire from fire aspect enchantment and took damage