I use Google Contacts and Calendars with my Lumia 920 (GDR2/Amber update) since beginning of 2013, so I'm one of the users, who access contacts and calendars still via Exchange Active Sync. I've always used two Google calendars, my main calendar and one with the birthdays of my contacts.
Since a couple of days my main calendar isn't shown anymore. It's available in the settings view, so I can enable or disable the calendar, but no appointments are shown. I've tried enabling and disabling the calendars, syncing, etc. but nothing helps.
I had this issue when I got my phone one year ago, but after a couple of syncs it worked.