This originates from MDL-73948.

If specific log entries are coming in out of order. ie the last one is now, and then another one appears from 5 seconds ago then it won't be picked up.

In the real world this will happen when any request takes longer than a second to be served, say N seconds, will buffer the event and send at shutdown and the event polling is 60 seconds. When ever N overlaps with 60 the event will be skipped. The fast you poll and the longer the delays the more you see the error.

Creds to brendanheywood