ZDLRA, ORA-17629: Cannot connect to the remote database server

In my customer Data Guard environment , rman backup use ZDLRA bi-directional architecture, both the primary and the standby databases are registered with the catalog.
Standby db DB_STBY1 connect to RA_stb catalog
Primary db DB_PRI1 connect to RA_pri catalog.
The databases are distinguished using the DB_UNIQUE_NAME in rman configuration.

CONFIGURE DB_UNIQUE_NAME 'DB_PRI1' CONNECT IDENTIFIER  'DB_PRI1';
CONFIGURE DB_UNIQUE_NAME 'DB_STBY1' CONNECT IDENTIFIER  'DB_STBY1';

It works fine so far ,but I got ORA-17629 error time to time ,it’s probably an oracle bug.

ORA-17629: Cannot connect to the remote database server during recync catalog.

In standby side, the resync catalog was failed duo to the primary protected database couldn’t connect to standby catalog .

In standby side , connect to standby DB and standby catalog , do resync catalog

oracle@:~/ [DB_STBY1] rman

RMAN> connect target sys/xxxxx

RMAN> connect catalog /@ra_stb-prod-iscan:1521/ra_stb

connected to recovery catalog database
recovery catalog schema version 21.01.00.00. is newer than RMAN version

RMAN> resync catalog

starting resync of recovery catalog
ORA-20079: full resync from primary database is not done        <===== need full resync from primary

starting resync from primary
resyncing from database with DB_UNIQUE_NAME DB_PRI              <===== resync from primary
RMAN-00571: ===========================================================
RMAN-00569: =============== ERROR MESSAGE STACK FOLLOWS ===============
RMAN-00571: ===========================================================
RMAN-03009: failure of resync command on default channel at 10/08/2021 09:59:41
ORA-17629: Cannot connect to the remote database server
ORA-17628: Oracle error 17629 returned by remote Oracle server
ORA-17629: Cannot connect to the remote database server

The workaround solution is doing resync catalog in primary db side directely. The primary protected database connect to standby catalog , run resync catalog.

IN primary side, connect to standby catalog

oracle:~/ [DB_PRI1] rman target / catalog /@ra_stb-prod-iscan:1521/ra_stb

RMAN> resync catalog;

starting full resync of recovery catalog
full resync complete

Then, run resync catalog in standby side again, it’s all fine.

In standby side,

oracle@:~/ [DB_STBY1] rman

RMAN> connect target sys/xxxxxx

connected to target database: DB_STBY1

RMAN>  connect catalog /@ra_stb-prod-iscan:1521/ra_stb

connected to recovery catalog database
recovery catalog schema version 21.01.00.00. is newer than RMAN version

RMAN> resync catalog

starting resync of recovery catalog
resync complete

RMAN> quit