I tried everything I found to solve: "NRPE: Unable to read output"

I've installed an NRPE in a server and I am testing with check_nrpe.

I've made this bash script /usr/local/nagios/libexec/example.sh:

ll /usr/local/nagios/libexec/example.sh
-rwxr-xr-x 1 root root 56 Sep 21 12:37 /usr/local/nagios/libexec/example.sh

cat 
#!/bin/bash

echo "WARNING: This is a test"
exit 1

The /usr/local/nagios/etc/nrpe.cfg file has this command defined:

command[example]=sudo /usr/local/nagios/libexec/example.sh

The /etc/sudoers.d/nrpe has these two lines:

nagios   ALL = NOPASSWD:/usr/local/nagios/libexec/example.sh
nrpe   ALL = NOPASSWD:/usr/local/nagios/libexec/example.sh

When I run:

/usr/local/nagios/libexec/check_nrpe -H 127.0.0.1 -c example

The output:

NRPE: Unable to read output

The log file(daemon mode):

[1663794786] CONN_CHECK_PEER: checking if host is allowed: 127.0.0.1 port 41351
[1663794786] Connection from 127.0.0.1 port 41351
[1663794786] is_an_allowed_host (AF_INET): is host >127.0.0.1< an allowed host >127.0.0.1<
[1663794786] is_an_allowed_host (AF_INET): host is in allowed host list!
[1663794786] Host address is in allowed_hosts
[1663794786] Host 127.0.0.1 is asking for command 'example' to be run...
[1663794786] Running command: sudo /usr/local/nagios/libexec/example.sh
[1663794786] Command completed with return code 1 and output:
[1663794786] Return Code: 3, Output: NRPE: Unable to read output
[1663794786] Connection from 127.0.0.1 closed.

Additional Information

• I tryed the root and the nagios/nrpe users to run check_nrpe(Both with same result).
• I attempted with echo "WARNING - ..." and echo "WARNING: ..." syntaxes.
• I checked each point mentioned in the NRPE: Unable To Read Output - Nagios Support page.
• I searched my issue in Google, the Nagios Forum, here... I didn't found or realize of anything wrong.
• I tried to run the command in the localhost, and from a remote Nagios Core Server, always the same issue.
• Obviously, the bash script runs okay in every environment... Including as a locally defined command in a Nagios Core Server.
• This command will work as a Nagios service.