As part of checking {T159795}, I created a page to be translated on https://meta.wikimedia.beta.wmflabs.org/wiki/Mavetuna (the page has 'Translate this page' link)
1. On [[ https://meta.wikimedia.beta.wmflabs.org/wiki/Mavetuna | Mavetuna]] page click on 'Translate this page' link.
2. Change the language to de and the translation can be started. However, typing anything in `tux-textarea-translation` will produce multiple errors in the Console:
```
Uncaught SyntaxError: Unexpected token < in JSON at position 0
```
3. Upon saving, the following warning will be displayed:
```
Saving the translation failed: This namespace is reserved for content page translations. The page you are trying to edit does not seem to correspond any page marked for translation.
```
Is this issue some sort of betalabs env limitation?