I'm also facing the same issue. Facts:
Using Windows 10 Edition (Bedrock)
Using Realms to play with my kid (me on PC, him on Switch)
A week ago, switched the world on Realms for a new one (to play in creative with my kid)
Then we decided to put the Survival world back on Realms
This swap between two worlds went for 2 or 3 times with no issues
Starting last week, I tried to swap for the survival world in Realms but got an error on -> "An error occurred" and nothing else
The Survival world works fine locally
Already tried to remove textures packs and mods (which are only 2 - Natural Texture pack and Lower Shield) but doesn't solve it
Tried to create a new realm and upload the world there but same issue
Tried last point after changing the world name without success
World size 208MB
Version 1.14.60 for both worlds
Both worlds were initially created in 1.14.60 as well
Restoring the survival world backups on Realms fails as well except backups prior to 16th of May (this is intriguing)
Downloaded the 16th of May backup world and if I try to uploaded to the second realm it fails with "An error occurred"
Downloaded the 16th of May backup world and if I try to uploaded to the first realm it also fails with "An error occurred"
Conclusion: world upload to realms seem to be broken somehow.
VouLT
I'm also facing the same issue. Facts:
Using Windows 10 Edition (Bedrock)
Using Realms to play with my kid (me on PC, him on Switch)
A week ago, switched the world on Realms for a new one (to play in creative with my kid)
Then we decided to put the Survival world back on Realms
This swap between two worlds went for 2 or 3 times with no issues
Starting last week, I tried to swap for the survival world in Realms but got an error on -> "An error occurred" and nothing else
The Survival world works fine locally
Already tried to remove textures packs and mods (which are only 2 - Natural Texture pack and Lower Shield) but doesn't solve it
Tried to create a new realm and upload the world there but same issue
Tried last point after changing the world name without success
World size 208MB
Version 1.14.60 for both worlds
Both worlds were initially created in 1.14.60 as well
Restoring the survival world backups on Realms fails as well except backups prior to 16th of May (this is intriguing)
Downloaded the 16th of May backup world and if I try to uploaded to the second realm it fails with "An error occurred"
Downloaded the 16th of May backup world and if I try to uploaded to the first realm it also fails with "An error occurred"
Conclusion: world upload to realms seem to be broken somehow.