Override a resolver for wp-graphql-acf v0.6.1 and older to prevent orphaned IDs from causing errors.

wp-graphql-acf-override-resolver.php

function _graphql_acf_sanitize_post_object_resolver( $value ) {

	if ( ! $value instanceof \WPGraphQL\Model\Post ) {
		return $value;
	}

	if ( 'publish' !== $value->status ) {
		return $value;
	}

}

add_filter( 'graphql_resolve_field', function( $default, $source, $args, $context, \GraphQL\Type\Definition\ResolveInfo $info, $type_name, $field_key, $field, $field_resolver ) {

	if ( ! isset( $info->fieldDefinition->config['acf_field']['type'] ) ) {
		return $default;
	}

	if ( 'post_object' !== $info->fieldDefinition->config['acf_field']['type'] ) {
		return $default;
	}

	if ( empty( $default ) ) {
		return $default;
	}

	if ( is_array( $default ) ) {
		return array_filter( array_map( '_graphql_acf_sanitize_post_object_resolver', $default ) );
	}

	return _graphql_acf_sanitize_post_object_resolver( $default );

}, 10, 9 );