I am not sure if it's a limitation of cx-testing environment.
When attempting to publish [[ http://cx-testing.wmflabs.org/index.php?title=Special:ContentTranslation&page=%D0%9F%D1%80%D0%B0%D0%B2%D0%B8%D0%BB%D1%8C%D0%BD%D1%8B%D0%B9+%D0%BC%D0%BD%D0%BE%D0%B3%D0%BE%D0%B3%D1%80%D0%B0%D0%BD%D0%BD%D0%B8%D0%BA&from=ru&to=en&targettitle=User%3AET1%2F%D0%9F%D0%BB%D0%B0%D1%82%D0%BE%D0%BD%D0%BE%D0%B2%D1%8B+%D1%82%D0%B5%D0%BB%D0%B0 | Правильный многогранник ]] to User:ET1/Платоновы тела (my test user space) I got
```
An error occurred while publishing the translation. Please try to publish the page again. Error: Error converting HTML to wikitext: docserver-http-error: (curl error: 28) Timeout was reached
```
The stack trace:
```
mw.Api error: docserver {error: {…}}
[CX] Error while publishing: docserver
{sourceLanguage: "ru", targetLanguage: "en", sourceTitle: "Правильный многогранник", sourceRevision: "87530953", targetTitle: "User:ET1/Платоновы тела", …}
error: {error: {…}}
sourceLanguage: "ru"
sourceRevision: "87530953"
sourceTitle: "Правильный многогранник"
targetLanguage: "en"
targetTitle: "User:ET1/Платоновы тела"
__proto__: Object
```
{F9633147}