woocommerce_checkout_order_processed hook priority not working between plguins

Question

I have a website with 2 plugins that use the woocommerce_checkout_order_processed hook. Plugin 1 uses the hook with priority 10 like so:

add_action('woocommerce_checkout_order_processed', [$this, 'add_delivery_data_to_order'], 10, 3);

and saves meta data to the order using:

$order->update_meta_data('test','true');
$order->save();

Plugin 2 uses the hook with priority 100 like so:

add_action('woocommerce_checkout_order_processed', [$this, 'get_delivery_data_to_order'], 100, 3);

and gets the meta data from the order using:

$order->get_meta_data();

For some reason Plugin 1 doesn't manage the save the data in time so when Plugin 2 tries to pull the meta data, it's empty.

Now, if I use the same hook from Plugin 1 in the child theme, it works. What could cause Plugin 1 not to be able to save the data on time?

Thanks