Example of how to fix the payment_url value for registration that have been imported using rhe importer add-on with partial payments.

tw_ee_payment_overview_url__query_args.php

<?php // Please do not include the opening PHP tag if you already have one

function tw_ee_payment_overview_url__query_args($query_args, $registration) {
	// Pull the transaction from the registration object.
	$transaction = $registration->transaction();
	// Check we have an EE_Transaction object
	// Check the 'attendee_information' step has NOT been complete
	// Check we have at least 1 payment related to the transaction
	// (likely an imported registration with attendee_information not set to true)
	if ($transaction instanceof EE_Transaction
		&& $transaction->reg_step_completed('attendee_information') !== true
		&& $transaction->get_first_related('Payment')
	) {
		// Change the query args to go to the payment_options.
		$query_args['step']    = 'payment_options';
		$query_args['revisit'] = true;
		$query_args['clear_session'] = true;
	}
	return $query_args;
}
add_filter( 'FHEE__EE_Registration__payment_overview_url__query_args','tw_ee_payment_overview_url__query_args', 20, 2);