For most people, it seems to be related to the number of devices attached to the hue bridge.
It looks like when they tested the change that went from polling the hue bridge every five minutes to polling every five seconds they tested with a bridge with about six devices connected. They definitely didn’t test with the Hue max of 50.
People start reporting problems between 15 and 25 devices. It just becomes too much message Traffic for The system to handle.