ssh connects okay from command line but from cron using publickey

To rsync (incremental) from remote server (Centos 6.x) to local client (Ubuntu 18.04) I copied the public key I created from client to server to execute rsync without password.

PasswordAuthentication yes at sshd_config

At local Ubuntu I have some executable scripts that look like

#!/bin/sh

RSYNC=/usr/local/bin/rsync-incr
SSH=/usr/bin/ssh\ -p\ xxxx
ROTATE=60
RUSER=yyyy
RHOST=zzzz
RPATH=/path-to-remote-dir/
LPATH=/path-to-local-dir/

$RSYNC -az --rsh="$SSH" $ROTATE $RUSER@$RHOST:$RPATH $LPATH

I run this script from command line /path-to-local-script-file

and it performs okay but if I add this line to crontab -e

00 00   * * *   /path-to-local-script-file

I get a cron error "Permission denied, please try again" when it is executed

Permission denied (publickey,gssapi-keyex,gssapi-with-mic,password).
rsync: connection unexpectedly closed (0 bytes received so far)
[Receiver] rsync error: unexplained error (code 255) at io.c(235) [Receiver=3.1.2]
*** ERROR: rsync returned code 255

Obviusly it is a permission issue. What I don't get is why I am able to execute /path-to-local-script-file from command line and perform rsync task successfully as user myname and cannot form cron (crontab -e executed as the same user.

Edit 1: I created a new key without passphrase, deleted the old rsa-ssh line with the public key from authorized_keys at remote server.
Same behavior, ok running script from command line, permission denied from cron

Edit 2:
Server log connecting ssh from command line

May 23 10:20:53 host sshd[21067]: Accepted publickey for root from xxx.xxx.6.13 port 42836 ssh2

May 23 10:20:53 host sshd[21067]: pam_unix(sshd:session): session opened for user root by (uid=0)

Server log connecting ssh from cron

May 23 10:17:03 host sshd[18163]: Failed password for root from xxx.xxx.6.13 port 42514 ssh2

May 23 10:17:03 host sshd[18163]: Failed password for root from xxx.xxx.6.13 port 42514 ssh2

May 23 10:17:03 host sshd[18164]: Connection closed by xxx.xxx.6.13