SCCM WSUS Sychn Failed

Hello everyone
I'm facing an issue of WSUS Sync Manager for many weeks.
the problem is that it's failing for some attemps and then without doing any change it succeeded in the next retry and it's always the same thing each day.
The first 02, 03 or 04 attemp failed and then it secceeded.
This is what i found:
from wsyncmgr.log:
Sync failed: The underlying connection was closed: The connection was closed unexpectedly. Source: Microsoft.UpdateServices.Internal.ApiRemoting.ExecuteSPGetParentCategories
STATMSG: ID=6703 SEV=E LEV=M SOURCE="SMS Server" COMP="SMS_WSUS_SYNC_MANAGER"  SITE= PID= TID= GMTDATE=mar. janv. 31 03:08:03.061 2023 ISTR0="Microsoft.UpdateServices.Internal.ApiRemoting.ExecuteSPGetParentCategories" ISTR1="The underlying connection was closed: The connection was closed unexpectedly" ISTR2="" ISTR3="" ISTR4="" ISTR5="" ISTR6="" ISTR7="" ISTR8="" ISTR9="" NUMATTRS=0 LE=0X80131509
Sync failed. Will retry in 60 minutes
from wcm.log:
Remote connection failed with exception 'System.Net.WebException: The underlying connection was closed: The connection was closed unexpectedly.~~   at Microsoft.UpdateServices.Administration.AdminProxy.CreateUpdateServer(Object[] args)~~   at Microsoft.SystemsManagementServer.SoftwareUpdatesManagement.WsusSyncAction.WSyncAction.DoSync()'. Attempting to bypass proxy
Sync failed: The underlying connection was closed: The connection was closed unexpectedly. Source: Microsoft.UpdateServices.Internal.ApiRemoting.ExecuteSPGetParentCategories
Sync failed. Will retry in 60 minutes
SCCM and WSUS are up to date with the last updates and configuration version.

If it was a proxy/FW, it'll be always blocked and i've checked the TLS 1.2 and it's OK.

Thanks in advance.

GH