Why Is my LaunchAgent not interacting with Time Machine Mac OSX

Question

I am currently writing an automation script for mac that takes control of time machine to run the backup at night. the script is wotking when running from a terminal, interaction as expected with time machine but when i try to run it using a launchDaemon the time machine command seems to be omitted. any idea why that is? Any help/insight would be greatly appreciated

the .plist file is root-owned and has a mod set at 600 (recommended by apple docs)

Here is the content of my .plist file:

    <?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN"
            "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
    <plist version="1.0">
        <dict>
            <key>Label</key>
            <string>local.automation</string>
            <key>ProgramArguments</key>
            <array>
                <string>/bin/bash</string>
                <string>/Users/<username>/<project>/automation.sh</string>
            </array>
            <key>RunAtLoad</key>
            <true/>
            <key>LaunchOnlyOnce</key>
            <true/>
        </dict>
    </plist>

the automation.sh file is also a root-owned file and the mod is set at 777. the content goes as follows:

    #!/bin/bash

    PASS=$(security find-generic-password -l 'root password' -a dl -w | tr -d '\n')
    echo "$PASS" | sudo -S tmutil disable