3689134 - DR_admin remote connection fails with Msg 4002 followed by Msg 11206 (no pb with sa) -SRS

DR_admin remote connection fails (no pb with sa)
"Error 11206 Unable to connect to server <SID>_Site1DR preceded  by 4002 Msg 4002 Login failed.

This message repeats every 10 seconds in the ASE error log at standby server (Site2), this is the SPID 18
00:0010:00000:00018:2025/11/27 10:43:37.73 server  background task error 4002: Login failed.
00:0010:00000:00018:2025/11/27 10:43:47.72 server  background task error 4002: Login failed.
00:0010:00000:00018:2025/11/27 10:43:57.72 server  background task error 4002: Login failed.

hostnameSite2% isql -UDR_admin -PXXXXXXXX -S<SID> -X -w2000

1> execute <SID>_Site1DR...sp_who
2> go
Msg 4002, Level 14, State 1:
Server '<SID>_Site1DR', Line 1:
Login failed.
Msg 11206, Level 16, State 1:
Server '<SID>', Line 1:
Unable to connect to server '<SID>_Site1DR'.

Customer is running HADR + DR system version 16.0 SP04 PL03

It seems that this error appeared since an unsuccessful failover attempt done on:
...
00:0002:00000:00455:2025/07/20 09:47:18.84 server  ** HADR operation: sap_failover Site1, Site2, 300
00:0002:00000:00455:2025/07/20 09:47:18.84 server  ** Message: failed
00:0002:00000:00455:2025/07/20 09:47:18.84 server  **********************************************************************************
00:0006:00000:00459:2025/07/20 09:47:25.62 server  Error: 11221, Severity: 16, State: 1
00:0006:00000:00459:2025/07/20 09:47:25.62 server  No external login for suserid 13, server name '<SID>_Site1DR'.
00:0006:00000:00459:2025/07/20 09:47:25.63 server  background task error 4002: Login failed.
...

SAP HADR 16.0 SP04 PL03

external login hadr_primarycheck_proc DE_admin remote connection 4002 11206 , KBA , BC-SYB-REP-SAP , Replication with SAP Suite / SAP BW , Problem