Upgrade operations may fail on a NetBackup Flex Scale cluster on which only media servers are deployed when an upgrade is performed from version 3.2 or 3.2.100 to version 3.5.100
If the API keys specified during cluster configuration on NetBackup Flex Scale version 3.0.0.1 are no longer valid on a cluster with media only deployment and if the setup has been upgraded to version 3.2 or 3.2.100, then an upgrade to version 3.5 may fail.
(IA-58149)
Workaround:
To resolve this issue, contact Veritas Technical Support and ask them to refer to article 100074130.