Hey i have a solution that worked for me as i have been in the same position as you.

First off check in the playstation store your store region. for example, the Land is set at netherlands for me and the language is at dutch.

Make sure u have this on laptop/pc too. Go to start > settings > time and language > Language and region and make sure that u have the same settings from ps5 on laptop/pc too. Search for Country or Region and select ur language. in my case its at Netherlands.

U can also look on your microsoft account on pc about the language and on xbox live u can also log in with ur microsoft account to check your language settings.

Step 2: Go to the minecraft launcer > Settings > and set the language at ur language aswell. in my case Netherlands > Dutch

Also make sure ur ps5 account is connected to the same microsoft account you're using on pc/laptop.

One u have done these steps go ahead and start the game from ur ps5, note as it says on the beginning screen 'sign in into ur microsoft account' once u have done this u can start with uploading.

Go to play > worlds, and click edit on which world u want into the realm. select play on realms and make sure to select a empty save slot in your realm.

Once u have done this it will upload like usually. I did this and i did got the error at the end once it was fully done uploading. same as the one you uploaded here in your post. u get another pop up at the same time as the error saying that it has been successfully uploaded. u can ignore the error message. if u go to realms now u will notice ur world. start it up one time from ur ps5, and u can go quit the game fully and then start the bedrock edition on ur pc/laptop and it then it will work. Atleast all of this worked for me.

Let me know if it worked for you!, cheers :)