"Allow save event to personal calendar" edit/Issue

Hi,
I have an issue with this item "allow save event to personal".
1- At first, admin text is in english, in my french version. The button is also in english. "save to" and not "sauver" or "noter".
2- I have created 3 events. structures are the same. Only one can be added to my personal Google Calendar. Two other only link to the calendar and don't create any new event into Google.

Any Idea ? Regard. Alain

I just fine issue.
When an event has a start date/hour but no end date/hour (because you don't know when it will end i.e.) Save to Google Calendar doesn't work.
You have to add an hour of end, even false one... And Google accept to save event in your personnal calendar.
I also translate "save to"...