I haven't looked into this at all yet, thought I would share it here first. Both my exit relays [0] received these repeated warnings around the same time yesterday:
timestamp [warn] Received http status code 404 ("Not found") from server 'server1IP:port' while fetching "/tor/keys/fp-sk/A1B2C3D4E5F6G7H8I9J0K1L2M3N4O5P6Q7R8S9T0-A1B2C3D4E5F6G7H8I9J0K1L2M3N4O5P6Q7R8S9T0". timestamp [warn] Received http status code 404 ("Not found") from server 'server2IP:port' while fetching "/tor/keys/fp-sk/A1B2C3D4E5F6G7H8I9J0K1L2M3N4O5P6Q7R8S9T0-A1B2C3D4E5F6G7H8I9J0K1L2M3N4O5P6Q7R8S9T0". timestamp [warn] Received http status code 404 ("Not found") from server 'server3IP:port' while fetching "/tor/keys/fp-sk/A1B2C3D4E5F6G7H8I9J0K1L2M3N4O5P6Q7R8S9T0-A1B2C3D4E5F6G7H8I9J0K1L2M3N4O5P6Q7R8S9T0". timestamp [warn] Received http status code 404 ("Not found") from server 'server4IP:port' while fetching "/tor/keys/fp-sk/A1B2C3D4E5F6G7H8I9J0K1L2M3N4O5P6Q7R8S9T0-A1B2C3D4E5F6G7H8I9J0K1L2M3N4O5P6Q7R8S9T0".
Only one timestamp and serverIP was consistent on both relays. All fingerprints, however, were consistent on both. Hasn't appeared before or since. Anything to worry about? Thanks.
[0] https://atlas.torproject.org/#details/799B025E25850A88CD133276301FAFB731C2EA...