When a person tries to translate an article already translated by him/her, the old translation shows up. This is perfectly normal and is not a bug in itself.
However, there have been at least two cases where the error message stating that the translation is based on an old version (which normally appears) does not appear properly. In one, the button to start the translation from the beginning does not appear, while in the other, the whole error message appear.
As far as I am aware of, pressing that button is the only way to translate an already published translation all over again (based on a newer edition).
note: another way to restart a translation could be a valid alternative (at least for me and one fellow translator)
relevant discussions on Talk:Content translation:
pages with problem
- West Midlands Trains English to Japanese
- Face masks during the COVID-19 pandemic English to French