Synology NAS is configured with community bluejay_monitor
(→ snmp.yml auth 'bluejay_v2'), not public. public_v2 was returning
HTTP 500 from snmp-exporter for this target. Verified bluejay_v2
returns metrics.
Keeps printer (10.0.58.107) on public_v2 — Epson ET-3750 uses
community "public" as documented in its SNMP settings.
CoreDNS iamworkin.lan template + ndots:5 was hijacking
unrealircd.irc.svc.cluster.local lookups → Traefik VIP → timeout.
Every alert since ~2026-04-09 silently failed with "IRC send failed: timed out",
which also killed the thermal-printer path (routed through irc-notify).
Same fix pattern as guacamole@28b7600.