Family Calendar syncs sporadically

I share a family calendar with my wife and son, but events only show up sporadically on each other's calendar. For example, I can see an event my wife set up on one date, but another of her events never shows up on my calendar. We've confirmed that we're using the same calendar, and that she's subscribed (I can see her name and email address with a green checkmark in the info next to the "Family" calendar under iCloud in the left-hand column) yet the calendar only seems to work some of the time. Any suggestions?