paramiko fails when used as cronjob

cront-tab :
SHELL=/usr/bin/bash
PATH=/home/user1/.local/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games:/snap/bin
HOME=/home/user1

52 * * * * bash -c "/home/user1/C++/scripts/BackUps.sh &> /home/user1/delete"

BackUps.sh :
#!/bin/bash
duplicity --no-encryption "/home/user1/Music" sftp://backU@192.168.1.151/Music

delete :
/usr/lib/python3/dist-packages/duplicity/backends/ssh_paramiko_backend.py:409: ResourceWarning: unclosed file <_io.TextIOWrapper name='/etc/ssh/ssh_config' mode='r' encoding='UTF-8'>
  sshconfig.parse(open(file))
ResourceWarning: Enable tracemalloc to get the object allocation traceback
BackendException: ssh connection to backU@192.168.1.151:22 failed: not a valid RSA private key file

BackUps.sh (using pexpect instead) :
#!/bin/bash
duplicity --no-encryption "/home/user1/Music" pexpect+sftp://backU@192.168.1.151/Music

delete (using pexpect) :
Local and Remote metadata are synchronized, no sync needed.
Last full backup date: Thu Feb 20 13:09:02 2020
--------------[ Backup Statistics ]--------------
StartTime 1582208643.30 (Thu Feb 20 16:24:03 2020)
EndTime 1582208643.31 (Thu Feb 20 16:24:03 2020)
ElapsedTime 0.00 (0.00 seconds)
SourceFiles 2
SourceFileSize 4029085 (3.84 MB)
NewFiles 0
NewFileSize 0 (0 bytes)
DeletedFiles 0
ChangedFiles 0
ChangedFileSize 0 (0 bytes)
ChangedDeltaSize 0 (0 bytes)
DeltaEntries 0
RawDeltaSize 0 (0 bytes)
TotalDestinationSizeChange 20 (20 bytes)
Errors 0
-------------------------------------------------

Description: Ubuntu 19.10
Release: 19.10
python3-paramiko:
  Installed: 2.6.0-1
  Candidate: 2.6.0-1
  Version table:
 *** 2.6.0-1 500
        500 http://gr.archive.ubuntu.com/ubuntu eoan/main amd64 Packages
        500 http://gr.archive.ubuntu.com/ubuntu eoan/main i386 Packages
        100 /var/lib/dpkg/status