[Закрытые] [PLEASE CONTINUE THE TOPIC] The translation progress cannot be saved beyond '69% complete'

Background of the issue:
[PLEASE CONTINUE THIS SUPORT AUTOMATICALLY CLOSED AGAIN] I am trying to progress the Chinese translation of a long English article using the classic translation editor. The article is located at скрытая ссылка. The current status is '69% complete'.

Symptoms:
I added translations for some sentences, marked them as 'Translation is complete', and clicked the 'Save' button. After reloading the page, the translated sentences were not saved, and the status reverted to '69% complete'.

Questions:
Why can't I save the translation progress beyond '69% complete'?
What does the 'WordPress database error Deadlock found' mean and how can I resolve it?
Should I clear any cache on the WPML Troubleshooting page?

I backup the database.