xPDOQuery sortby (bug?)

$c = $modx->newQuery('erCategories');
$c->where(array('menu_id' => $mid,'active' => 1,));
$c->sortby($sort,$dir);

$c->construct(); return $c->toSQL();

SELECT `erCategories`.`id` AS `erCategories_id`, 
`erCategories`.`name` AS `erCategories_name`, 
`erCategories`.`description` AS `erCategories_description`, 
`erCategories`.`image` AS `erCategories_image`, 
`erCategories`.`position` AS `erCategories_position`, 
`erCategories`.`menu_id` AS `erCategories_menu_id`, 
`erCategories`.`active` AS `erCategories_active` 
FROM `modx_easyrestaurant_categories` AS `erCategories` 
WHERE ( `erCategories`.`menu_id` = 1 
AND `erCategories`.`active` = 1 ) ORDER BY id ASC

$c = $modx->newQuery('erCategories');
$c->where(array('menu_id' => $mid,'active' => 1,));
$c->sortby('erCategories_id',$dir);

$sort = $modx->getOption('sort',$scriptProperties,'erCategories_id');
$dir = $modx->getOption('dir',$scriptProperties,'ASC');

<?xml version="1.0" encoding="UTF-8"?>
<model package="easyrestaurant" baseClass="xPDOObject" platform="mysql" defaultEngine="MyISAM">
	<object class="erMenus" table="easyrestaurant_menus" extends="xPDOSimpleObject">
		<field key="name" dbtype="varchar" precision="255" phptype="string" null="false" default=""/>
        <field key="description" dbtype="text" phptype="string" default=""/>
		<field key="image" dbtype="varchar" precision="255" phptype="string" default=""/>
		<field key="resource_id" dbtype="int" precision="10" phptype="integer" default="0" />r
		<field key="active" dbtype="tinyint" precision="1" phptype="integer" default="1"/>
		
		<composite alias="menuCategories" class="erCategories" local="id" foreign="menu_id" cardinality="many" owner="local" />
		<composite alias="menuItems" class="erItems" local="id" foreign="menu_id" cardinality="many" owner="local" />
		<composite alias="resourceId" class="modResource" local="resource_id" foreign="id" cardinality="one" owner="foreign"/>	
	</object>

	<object class="erCategories" table="easyrestaurant_categories" extends="xPDOSimpleObject">
		<field key="name" dbtype="varchar" precision="255" phptype="string" null="false" default=""/>
        <field key="description" dbtype="text" phptype="string" default=""/>
		<field key="image" dbtype="varchar" precision="255" phptype="string" default=""/>
		<field key="position" dbtype="int" precision="10" phptype="integer" default="0" />
		<field key="resource_id" dbtype="int" precision="10" phptype="integer" default="0" />
		<field key="active" dbtype="tinyint" precision="1" phptype="integer" default="1"/>
		
		<aggregate alias="menuResource" class="modResource" local="resource_id" foreign="id" cardinality="one" owner="foreign" />
		<composite alias="menuItems" class="erItems" local="id" foreign="cat_id" cardinality="many" owner="local" />		
	</object>
	
    <object class="erItems" table="easyrestaurant_items" extends="xPDOSimpleObject">
		<field key="name" dbtype="varchar" precision="255" phptype="string" null="false" default=""/>
        <field key="description" dbtype="text" phptype="string" default=""/>
        <field key="price" dbtype="varchar" precision="255" phptype="string" default=""/>
        <field key="image" dbtype="varchar" precision="255" phptype="string" default=""/>
        <field key="featured" dbtype="tinyint" precision="1" phptype="integer" default="0"/>
		<field key="cat_id" dbtype="int" precision="10" phptype="integer" default="0" />
		<field key="menu_id" dbtype="int" precision="10" phptype="integer" default="0" />
        <field key="position" dbtype="int" precision="10" phptype="integer" default="0" />
		<field key="active" dbtype="tinyint" precision="1" phptype="integer" default="1"/>

		<aggregate alias="menuCategories" class="erCategories" local="cad_id" foreign="id" cardinality="one" owner="foreign" />
    </object>
</model>

<?php
$easyrestaurant = $modx->getService('easyrestaurant','Easyrestaurant',$modx->getOption('easyrestaurant.core_path',null,$modx->getOption('core_path').'components/easyrestaurant/').'model/easyrestaurant/',$scriptProperties);
if (!($easyrestaurant instanceof Easyrestaurant)) return '';

/* setup default properties */
$resid = $modx->resource->get('id');
$tpl = $modx->getOption('tpl',$scriptProperties,'rowTpl');
$outertpl = $modx->getOption('outertpl',$scriptProperties,'outerTpl');
$cattpl = $modx->getOption('cattpl',$scriptProperties,'catTpl');
$sort = $modx->getOption('sort',$scriptProperties,'position');
$dir = $modx->getOption('dir',$scriptProperties,'ASC');
$menuid = $modx->getOption('menuid', $scriptProperties,$resid);
$showinactive = $modx->getOption('showinactive',$scriptProperties,0);
$separator = $modx->getOption('separator',$scriptProperties,"\n");
$catSeparator = $modx->getOption('categorySeparator',$scriptProperties,"\n");

$output = '';

/* run db query */
$sort = "erCategories_" . $sort; // Weird debug necessary to get sortby running

$c = $modx->newQuery('erCategories');
$c->where(array('resource_id' => $menuid));
if($showinactive == 0) $c->where(array('active' => 1));
$c->sortby($sort,$dir);
//$c->construct(); return $c->toSQL();
$categories = $modx->getCollection('erCategories', $c );

$output = array();
foreach ($categories as $category) {
	$cats = array();
	$sort = $modx->getOption('sort',$scriptProperties,'position');
	$sort = "erItems_" . $sort;
	$catid = $category->get('id');
	$c = $modx->newQuery('erItems');
	$c->where(array('cat_id' => $catid));
	if($showinactive == 0) $c->where(array('active' => 1));
	$c->sortby($sort,$dir);
	$items = $modx->getCollection('erItems', $c );
    if(count($items) >=1) {
		$categoryArray = $category->toArray();
		$cats[] = $easyrestaurant->getChunk($cattpl,$categoryArray);
	}
	
	foreach ($items as $item) {
		$itemArray = $item->toArray();
		$cats[] = $easyrestaurant->getChunk($tpl,$itemArray);
	}
	
	$cats = implode($separator,$cats);
	$output[] = $cats;	
}
$output = implode($catSeparator,$output);

$output = $easyrestaurant->getChunk($outertpl,array('wrapper' => $output));

return $output;