One of my guard relays has a few entries on Oct 06 also:
Oct 06 09:04:00.000 [warn] Duplicate rendezvous cookie in ESTABLISH_RENDEZVOUS. Oct 06 09:04:00.000 [warn] Duplicate rendezvous cookie in ESTABLISH_RENDEZVOUS. Oct 06 10:17:30.000 [warn] Duplicate rendezvous cookie in ESTABLISH_RENDEZVOUS.
Times are in UTC. Logs on this machine go back to Oct 03 but those are the only occurrences. My other guard relay with nearly identical specs and CW doesn't have these entries.