I have contact MojangSupport on twitter and sent an email to Mojang Support too.
The level of customer service I'm getting for a paid service is worryingly poor.
Is there an ETA for this?
There is nowhere in the Realms system for me to download logs.
I've set the security to private because I am not sharing my world with the world.
It's a realms server, where do I obtain the logs from?
You also closed my issue as a duplicate. This was happening on REALMS with vanilla client.
It was solved by deleting the DIM1/ folder in the save and then re-uploading. How it was caused is still unknown.
Given that I've had to find a solution to my own problem, I'm very unhappy with the level of "service" offered by Realms. It is simply not good enough to expect the community to work things out when you've paid for a product.