Serious Performance Problems during Time Machine Backup to Synology NAS (SMB)

• MacBook Pro 16" 2021, M1 Max, 64 GB
• macOS Ventura 13.3
• Synology DS220+, DSM 7.1.1

I am backing up my MacBook Pro with Time Machine to three different medias (2 x USB and 1 x Synology NAS). The USB backups work all perfectly. But during the backup to the Synology NAS, the MacBook Pro 2021 ist very slow and often shows the spinning wheel or locks completely for several seconds. The backup process is very slow, despite the 1GB network.

I suspect that the problem lies in the SMB, but I do not want to enable the out-of-service AFP protocol. The SMB statistics during the backup process are:

==================================================================================================
SHARE                         ATTRIBUTE TYPE                VALUE
==================================================================================================
Time Machine Backups          
                              SERVER_NAME                   K43-NAS._smb._tcp.local.
                              USER_ID                       0
                              SMB_NEGOTIATE                 SMBV_NEG_SMB1_ENABLED
                              SMB_NEGOTIATE                 SMBV_NEG_SMB2_ENABLED
                              SMB_NEGOTIATE                 SMBV_NEG_SMB3_ENABLED
                              SMB_VERSION                   SMB_3.1.1
                              SMB_ENCRYPT_ALGORITHMS        AES_128_CCM_ENABLED
                              SMB_ENCRYPT_ALGORITHMS        AES_128_GCM_ENABLED
                              SMB_ENCRYPT_ALGORITHMS        AES_256_CCM_ENABLED
                              SMB_ENCRYPT_ALGORITHMS        AES_256_GCM_ENABLED
                              SMB_CURR_ENCRYPT_ALGORITHM    OFF
                              SMB_SHARE_TYPE                DISK
                              SIGNING_SUPPORTED             TRUE
                              EXTENDED_SECURITY_SUPPORTED   TRUE
                              UNIX_SUPPORT                  TRUE
                              LARGE_FILE_SUPPORTED          TRUE
                              OS_X_SERVER                   TRUE
                              FILE_IDS_SUPPORTED            TRUE
                              QUERYINFO_NOT_SUPPORTED       TRUE
                              DFS_SUPPORTED                 TRUE
                              FILE_LEASING_SUPPORTED        TRUE
                              MULTI_CREDIT_SUPPORTED        TRUE

Is the SMB broken in macOS or are there any configuration changes which could help?

Thank you.

Andy Brunner