HGST user manual. page 71 onwards is relevant -
https://www.hgst.com/sites/default/files/resources/4U60-G2-Storage-Enclosure-User-Guide.pdf
maybe someone changed some of the settings in the management interface. Page 72 shows how to use the ethernet management interface. Looking at the list of commands it supports iomconfiguration should be set to dual and the other command that stands out is zonecfg which should be disabled. I havn't connected mine up yet
ok so my enclosure firmware is: 0210 based on what lsscsi says
i installed sg3-utils and lsscsi packages with apt-get then ran:
sudo lsscsi -g | grep encl
output which shows both backplanes:
[0:0:24:0] enclosu HGST 4U60_STOR_ENCL 0210 - /dev/sg24
[8:0:2:0] enclosu HGST 4U60_STOR_ENCL 0210 - /dev/sg27
see what firmware your enclosure is running. Based on the manual if we can get a copy of the firmware from HGST you can downgrade flash it. I don't see a way for me to read/save the firmware
also i ran sg_scan to show all the devices i have running that the sas card sees and I'm at 28 right now:
sudo sg_scan
/dev/sg0: scsi0 channel=0 id=0 lun=0
etc with 27 more entries