Wordpress custom meta not updating from a custom Setting Panel in Gutenberg

Question

I am trying to make a custom post setting panel in gutenberg with custom meta to save my options, but the meta is not updating correctly.

I am using a dropdown with custom values and the meta gets saved on the first save, BUT if I change the value of the dropdown again, and click click save, it won't actually update the meta in the database and will show the previous value after I refresh the page.

How to do ? Thanks

Here is my code :

I register my custom meta with php:

function myguten_register_post_meta() {
        register_post_meta('post', 'my_custom_meta', [
            'show_in_rest' => true,
            'single' => true,
            'type' => 'string',
            'auth_callback' => function() {
                return current_user_can('edit_posts');
            }
        ]);
}

add_action( 'init', 'myguten_register_post_meta' );

And the JS:

const { registerPlugin } = wp.plugins;

import My_Custom_Panel from './my-custom-panel';

const MyPanel= () => {
    return (
        <My_Custom_Panel  />
    );
}

registerPlugin('my-custom-panel', {
    render: MyPanel,
    icon: 'format-image', 
});

my-custom-panel.js:

const { __ } = wp.i18n;
const { useSelect, useDispatch } = wp.data;
const { PluginDocumentSettingPanel } = wp.editPost;
const { PanelRow, SelectControl } = wp.components;

const My_Custom_Panel = () => {

    const templateId = useSelect((select) =>
        select('core/editor').getEditedPostAttribute('meta')['my_custom_meta']
    );

    const { editPost } = useDispatch('core/editor');

    return (
        <PluginDocumentSettingPanel
            name="my-panel"
            title="My Panel"
            className="my-panel"
        >
            <PanelRow>
                <SelectControl
                    label={__('Select template...', 'txtdomain')}
                    value={templateId}
                    onChange={(value) => editPost({ meta: { my_custom_meta: value } })}
                    options={[
                        { label: "tpl 1", value: "t1" },
                        { label: "tpl 2", value: "t2" },
                        { label: "tpl 3", value: "t3" },
                    ]}
                />
            </PanelRow>
        </PluginDocumentSettingPanel>
    )
};

export default My_Custom_Panel ;