Can't mount image

hi. i’ve found a bunch of similar issues here but they weren’t helpful for me unfortunately. so, any help is appreciated.

the server is Oracle Linux 7.9.

# rpm -q urbackup-server
urbackup-server-2.5.37.0-1.2.x86_64

# cat /etc/fuse.conf
# mount_max = 1000
user_allow_other

# systemctl cat urbackup-server
# /usr/lib/systemd/system/urbackup-server.service
[Unit]
Description=UrBackup Client/Server Network Backup System
After=syslog.target network.target

[Service]
ExecStart=/usr/bin/urbackupsrv run --config /etc/sysconfig/urbackup-server --no-consoletime
User=root
TasksMax=infinity

[Install]
WantedBy=multi-user.target


# /etc/systemd/system/urbackup-server.service.d/override.conf
[Service]
StandardOutput=null
StandardError=null
Environment=LIBGUESTFS_BACKEND=direct

an attempt to mount an image from the web ui throws the error:

Mounting image failed. Please see server log file for details.
Loading FUSE kernel module... Starting VHD background process... Waiting for background process to become available... Mounting... libvirt: XML-RPC error : Cannot recv data: Connection reset by peer libguestfs: error: could not connect to libvirt (URI = qemu:///session): Cannot recv data: Connection reset by peer [code=38 int1=104] Mounting failed. UrBackup mount process returned non-zero return code 

along with the error in the server’s log:

2026-06-24 10:23:18: ERROR: Image mounting failed: Loading FUSE kernel module...
Starting VHD background process...
Waiting for background process to become available...
Mounting...
libvirt: XML-RPC error : Cannot recv data: Connection reset by peer
libguestfs: error: could not connect to libvirt (URI = qemu:///session): Cannot recv data: Connection reset by peer [code=38 int1=104]
Mounting failed.
UrBackup mount process returned non-zero return code

the following processes are running at that moment:

urbackup 15280     1  0 10:16 ?        00:00:03 /usr/bin/urbackupsrv run --config /etc/sysconfig/urbackup-server --no-consoletime
root     18043     1  0 10:23 ?        00:00:00 /usr/bin/urbackupsrv mount-vhd -f /btrfs/Sorento/260617-0001_Image_C/Image_C_260617-0001.vhdz -m /btrfs/Sorento/260617-0001_Image_C/contents0 -t /btrfs/Sorento/260617-0001_Image_C/device0 -o uid=991,gid=987,allow_root --guestmount

i can mount the image from the shell, though:

# LIBGUESTFS_BACKEND=direct /usr/bin/urbackupsrv mount-vhd   -f /btrfs/Sorento/260617-0001_Image_C/Image_C_260617-0001.vhdz   -m /mnt/
Loading FUSE kernel module...
Starting VHD background process...
Waiting for background process to become available...
Mounting...
Mounted successfully.

please, help!

PS unmounting /mnt does not stop the process:

# mount | grep /mnt
# ps -ef|grep mnt
root     20586     1  0 10:26 ?        00:00:00 /usr/bin/urbackupsrv mount-vhd -f /btrfs/Sorento/260617-0001_Image_C/Image_C_260617-0001.vhdz -m /mnt/