Failed To Sync World Data - Minecraft

I was having trouble with my Xbox One and contacted their support to try and fix a microphone issue. They told me to perform a "Reset and keep my games & apps". Since then, now I've re-enabled all our
accounts, 2 of my worlds on Minecraft say (following an attempt to sync them) "The world is not fully synced or has been corrupted. Try playing the world on a console where it's in a good state and try migrating it again." How can I retrieve these 2 worlds?

I've tried:

- Performing a power cycle - did not resolve issue

- Deleting my profile from xbox and signing back in - did not resolve issue

- Clearing local saved games - did not resolve issue

- Reset and keep my games & apps - caused the issue, I'm reluctant to try that again!

I've seen other suggestions about uninstalling Minecraft and re-installing it, but I don't want to cause further issues and the reports seem to indicate that doesn't work anyway.

What can I do?!

I've contacted Mojang support and waited a month to be told:

Code:

First of all, I'd like to apologize for the late reply due to our backlog. 

I'm sorry to hear that you're having trouble with your game. Unfortunately, this help center is limited mostly to accounts and billing; we do not have a technical support team.

If you're having trouble with the PC/Java edition of Minecraft, you may want to visit our list of resources at https://help.mojang.com/customer/portal/articles/1175661, which contain a community help chat,
forums, and a crash lookup tool.

For all other Minecraft editions and Mojang games, please visit https://help.mojang.com/customer/portal/articles/364794.
At a loss o know what to do... I know now I should have backed up the worlds and made copies so please don't just comment about what a noob I am!!!

:)