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 .220.127.116.11.4.1.6518.104.22.168.5:
Karaf Shell polling while drive 5 down: