It's a Synology with 5 drives in a RAID. Drive 5 has an outage (see snmpwalk). The poller should walk the OID tree and if one entry doesn't match "1" it should go offline. But it didn't.
Snmpwalk on .188.8.131.52.4.1.65184.108.40.206.5:
Karaf Shell polling while drive 5 down: