HPDM 4.7 Service Pack 5 just got released which includes additional checks while the Agent upgrade.
Can you try to upgrade to SP-5 and then do the Agent Update on one of the units that still has a working older Agent?
Tests in my lab show successful on where I encountered a similar issue on a customer image but the issue being gone after using SP-5.
ftp://ftp.hp.com/pub/hpdm/Software/4.7/HP_Device_Manager-4.7SP5.zip
ftp://ftp.hp.com/pub/hpdm/Documentation/ReleaseNotes/ReleaseNotes_HP_Device_Manager-4.7SP5.pdf
