Avamar: Oracle Backup channels being disabled during RMAN backups: channel disabled, job failed on it will run on another channel

RMAN-03009: failure of backup command on t6 channel at %date%
ORA-19509: failed to delete sequential file, handle="Instance", parms="SBT_LIBRARY=/usr/local/avamar/lib/libobk_avamar64.so,ENV=(ORACLE_HOME=/path/to/db_home"
ORA-27027: sbtremove2 returned error
ORA-19511: non RMAN, but media manager or vendor specific failure, error text:
   getinfo() returned error:-2 labelnum:0 local_error:-1
ORA-27191: sbtinfo2 returned err
channel t6 disabled, job failed on it will be run on another channel
RMAN-03009: failure of backup command on t7 channel at %date%

avtar Warning : Cannot write dispatcher table file /usr/local/avamar/var/client_name-27000.dtb (code 13: Permission denied).
avtar Info : - Trying connection Utility_node:29000
avtar Info : - Connected to node Utility_node:29000, Priv=0, SSL Cipher=ECDHE-RSA-AES256-GCM-SHA384
avtar Info : Login User: "dbarman", Domain: "default", Account: "/domain/client_name
avtar Info : Logging in on connection 0 (server 0)
avtar Error : Login error 74: Account not found in the Avamar database
avtar FATAL : Failed to initiate session with server
avtar Info : Error summary: 2 errors: 5308, 5126
avtar Info : Command failed (2 errors, 1 warning, exit code 10008: cannot establish connection with server (possible network or DNS failure))

--pidname=Oracle
--pidnum=pidnum
--logfile=install-dir/var/clientlogs/avtar.log
--vardir=install-dir/var/clientlogs
--id=user
--ap=password
--path=/clients/my-db-client