Kendo DataViz grouping problem

HTML

<script src="http://cdn.kendostatic.com/2013.3.1119/js/kendo.all.min.js"></script>
Not grouped correctly:
<div id="my-chart-1"></div>
Different data, grouped OK:
<div id="my-chart-2"></div>

JavaScript

var chartData1 = [{
       "site": "10-200",
        "product_group": "Automotive Mfg",
        "inventory_turns": 2.129988
}, {
    "site": "10-202",
        "product_group": "Automotive Mfg",
        "inventory_turns": 14.404241
}, {
    "site": "10-301",
        "product_group": "Automotive Mfg",
        "inventory_turns": 0.000000
}, {
    "site": "10-150",
        "product_group": "Automotive Mfg",
        "inventory_turns": 0.000000
}, {
    "site": "30-200",
        "product_group": "Automotive Mfg",
        "inventory_turns": 20.243573
}, {
    "site": "30-202",
        "product_group": "Automotive Mfg",
        "inventory_turns": 0.000000
}, {
    "site": "30-301",
        "product_group": "Automotive Mfg",
        "inventory_turns": 29.167412
}, {
    "site": "30-150",
        "product_group": "Automotive Mfg",
        "inventory_turns": 24.934668
}, {
    "site": "20-200",
        "product_group": "Automotive Mfg",
        "inventory_turns": 22.129988
}, {
    "site": "20-202",
        "product_group": "Automotive Mfg",
        "inventory_turns": 24.404241
}, {
    "site": "20-301",
        "product_group": "Automotive Mfg",
        "inventory_turns": 10.000000
}, {
    "site": "20-150",
        "product_group": "Automotive Mfg",
        "inventory_turns": 10.000000
}, {
    "site": "40-200",
        "product_group": "Automotive Mfg",
        "inventory_turns": 10.243573
}, {
    "site": "40-202",
        "product_group": "Automotive Mfg",
        "inventory_turns": 10.000000
}, {
    "site": "40-301",
        "product_group": "Automotive Mfg",
        "inventory_turns": 19.167412
}, {
    "site": "40-150",
        "product_group": "Automotive Mfg",
        "inventory_turns": null
},{
"site": "10-200",
        "product_group": "Food &amp; Bev Mfg site",
        "inventory_turns": null
}, {
    "site": "10-202",
        "product_group": "Food &amp; Bev Mfg site",
        "inventory_turns": null
}, {
    "site": "10-301",
        "product_group": "Food...