We have the same "issue", BUT I was explained that it's the time that relay is syncing that the calendar comes down then goes back up.
Basically, the listener is on constant contact with the calendars. The relay controls the polycom calendar.
When the relay and listener are syncing, the relay pulls the polycom calendar down, once the relay and listener are in sync then relay pushes the updated calendar to the polycom.
For us, we see the calendar come down for about 25-45 seconds. I haven't been able to pinpoint the interval that it does the sync, it seems random.
If the above is incorrect, I would appreciate help from BlueJeans as well on this.