S7 : My 'All calendars' tab under Manage Calendars won't stay on

[Android Central Question]

Have had no problems syncing my Google calendar with my wife's - until recently.
I can receive her entries , she can't see mine.
Solution seems to be to open Samsung Calendar and set the 'All Calendar' tab to on.

Tried to set the 'All Calendars' tab to on. Exit . Open Samsung Calendar , Got to Manage Calendar and the tab under 'All Calendars ' is reset to OFF.

This happens after I go into Google Calendars to enter a test entry.

Only hint is that 'Contacts' under Manage Calendars seems to also switch off.