Nothing happens for several hours during the backup

Hello there,
We have an urbackup Server and an urbackup client (both centos).
Unfortunately, the backups take a very long time.
In the logs I can see, that nothing happens for several hours.

Info
25.05.22 02:25
Starting scheduled incremental file backup…
Info
25.05.22 02:35
Backing up “lotus” without snapshot.
Info
25.05.22 02:35
Following symbolic link at “/lotus/notesdata/domino/adm-bin/acls” to “/opt/hcl/domino/notes/12000100/linux/execbin” confirms symlink backup target “.symlink_execbin_1” to “/opt/hcl/domino/notes/12000100/linux/execbin”
Info
25.05.22 02:35
Indexing of “lotus” done. 2111 filesystem lookups 0 db lookups and 264 db updates
Info
25.05.22 02:35
Backing up “.symlink_execbin_1” without snapshot.
Info
25.05.22 02:35
host01: Loading file list…
Info
25.05.22 02:35
host01: Calculating file tree differences…
Info
25.05.22 02:35
host01: Calculating tree difference size…
Info
25.05.22 02:35
host01: Linking unchanged and loading new files…
Info
25.05.22 02:35
Referencing snapshot on “host01” for path “lotus” failed: FAILED
Info
25.05.22 07:45
Waiting for file transfers…

There are 5 hours between "Referencing snapshot " and “Waiting for file transfer”.
I am surprised that it tries to reference a snapshot even though it is disabled.

It would be wonderful if someone could help me.