jQuery Grid Plugin - jqGrid

Hello, I've been working with jqGrid 3.6.2 for a couple of days and noticed that I was not getting the pagination I expected. Here is my options object:

var options = {

            jsonReader : { 

               root: "items", 

               page: "page",        // pager

               total: "total",      // pager

               records: "numRows",  // pager

               repeatitems: false, 

               cell: "items", 

               id: "inv_num",

               userdata: "PHPSESSID"

            },

            prmNames: {

                page:'page',

                rows:'count',

                sort:'sort'

            },

[...postData and colModel here...]

            mtype: 'GET',

            colNames:['Inv #'],

            datatype:"json",

            height: '200',

            autowidth: true,

            shrinkToFit: true,

            scroll: true,

            sortname:'inv_num',

            sortorder:"desc",

            loadui: 'block',

            altRows: true,

            page: 1,

            scrollrows: true,

            url:'file.php'

};

Notice that my 'page' option is set to 1. I realize that this is the default. I noticed that on a data set that had 45 records, displaying 20 records would mean 3 pages (1-20, 21-40, 41-45). I noticed that when scrolling down, I could get page 1 and I could get page 2, but I could not get page 3. I thought perhaps this was due to my pagination calculation, so I changed 'page' to zero hoping it would fix the issue, but instead I observed getting page 0, then page 2, I was never able to get page 1.

I went back to page = 1 and  manually increased my response to say that the total pages was 3+1. From there I was able to get page 1, 2 and 3. 

I looked around in grid.base.js and found where it was (I think) calculating whether or not to grab another page. I found this condition on line 273 of that file:

(ttop <= 0 && tbot < dh && 

                    (p.lastpage==null||parseInt((tbot + scrollTop + div - 1) / div) < p.lastpage))

If I changed the operator to: '<= p.lastpage', I was able to get all of my pages leaving page = 1.

Can anyone confirm that this is an error, or am I doing something incorrectly? The only way I could further test was to verify that in fact the request for the last page was never actually being sent out. Making this change also fixed a spacing issue at the bottom of my grid (I presume to be height related?).