We know that the save requests were coming from a single user. It would be helpful to try to contact this person to learn more. For example if the person noticed any weird, or what browser etc.
She was translating the article https://en.wikipedia.org/wiki/Doaba from English to Bengali when CX caused an infrastructure incident and was turned off for a while until Niklas put in an API ping limiter. I verified with her about what she was trying to do on that day. She mentioned that she had installed Google Chrome a few days earlier and started using it instead of Chromium. Although our logs showed her as using Chrome v 34, the version present on her laptop currently is > v 51. On that particular day she remembers that for a very long time she saw an error about "reloading the saved translation" and could not continue translation for many hours. However, she could not remember if she had closed the tab and tried to reopen an ongoing translation.