Identically configured checkbox form elements produce identical HTML code but display differently

I'm simplifying my site's Registration page to make it quicker and easier for new users to register for a new user account.

I'm using Zend and PHP and I have a really strange problem:

• 4 checkboxes, created identically
• The first two display fine
• The second two display in a broken format (described below)

Tried the following:

• Moving the working checkboxes around the page - They continue to work.
• Moving the broken checkboxes around the page - They continue to fail.
• Refreshing browser cache.
• Restarted apache
• Doing a text comparison to ensure that all code is identical.

This is driving me nuts. Any help would be much appreciated!

PHP form definition:

    $this->addElement('checkbox','user_working1',array(
        'label'=>'    I am working1',
        "class"      => "form-control hoverToolTip",
        "required"   => false,
    ));



    $this->addElement('checkbox','user_working2',array(
        'label'=>'    I am working2',
        "class"      => "form-control hoverToolTip",
        "required"   => false,
    ));


    $this->addElement('checkbox','user_broken3',array(
        'label'=>'I am broken3',
        "class"      => "form-control hoverToolTip",
        "required"   => false,
    ));


    $this->addElement('checkbox','user_broken4',array(
        'label'=>'    I am broken4',
        "class"      => "form-control hoverToolTip",
        "required"   => false,          
    ));     

PHP view:

<div class="row margin-0">
    <div class="col-sm-4 col-md-3">
        <div class="">
            <h4 class="form-signin-heading">
                Professional Profile&nbsp; <i class="fa fa-briefcase"></i>
            </h4>

        </div>
    </div>
    <div class="col-sm-8 col-md-9">
        <div class="row">
            <div class="col-sm-6">
                <div class="input-group form-group">
                        <?php echo $this->form->user_working1?> 
                    </div>
            </div>
            <div class="col-sm-6">
                <div class="input-group form-group"> 
                        <?php echo $this->form->user_working2?> 
                    </div>
            </div>
        </div>
    </div>
</div>

<div class="row margin-0">
    <div class="col-sm-4 col-md-3">
        <div class="">
            <h4 class="form-signin-heading">
                Professional Profile&nbsp; <i class="fa fa-briefcase"></i>
            </h4>

        </div>
    </div>
    <div class="col-sm-8 col-md-9">
        <div class="row">
            <div class="col-sm-6">
                <div class="input-group form-group">
                        <?php echo $this->form->user_broken3?> 
                    </div>
            </div>
            <div class="col-sm-6">
                <div class="input-group form-group"> 
                        <?php echo $this->form->user_broken4?> 
                    </div>
            </div>
        </div>
    </div>
</div>

HTML output:

    <div class="row margin-0">
        <div class="col-sm-4 col-md-3">
            <div class="">
                <h4 class="form-signin-heading">
                    Professional Profile&nbsp; <i class="fa fa-briefcase"></i>
                </h4>

            </div>
        </div>
        <div class="col-sm-8 col-md-9">
            <div class="row">
                <div class="col-sm-6">
                    <div class="input-group form-group">
                            <div class=" form-group "><label for="user_working1" class="optional">&nbsp;&nbsp;&nbsp;&nbsp;I am working1</label>

<input type="hidden" name="user_working1" value="0"><input type="checkbox" name="user_working1" id="user_working1" value="1" class="form-control hoverToolTip"></div> 
                        </div>
                </div>
                <div class="col-sm-6">
                    <div class="input-group form-group"> 
                            <div class=" form-group "><label for="user_working2" class="optional">&nbsp;&nbsp;&nbsp;&nbsp;I am working2</label>

<input type="hidden" name="user_working2" value="0"><input type="checkbox" name="user_working2" id="user_working2" value="1" class="form-control hoverToolTip"></div> 
                        </div>
                </div>
            </div>
        </div>
    </div>



    <div class="row margin-0">
        <div class="col-sm-4 col-md-3">
            <div class="">
                <h4 class="form-signin-heading">
                    Professional Profile&nbsp; <i class="fa fa-briefcase"></i>
                </h4>

            </div>
        </div>
        <div class="col-sm-8 col-md-9">
            <div class="row">
                <div class="col-sm-6">
                    <div class="input-group form-group">
                            <div class=" form-group "><label for="user_broken3" class="optional">&nbsp;&nbsp;&nbsp;&nbsp;I am broken3</label>

<input type="hidden" name="user_broken3" value="0"><input type="checkbox" name="user_broken3" id="user_broken3" value="1" class="form-control hoverToolTip"></div> 
                        </div>
                </div>
                <div class="col-sm-6">
                    <div class="input-group form-group"> 
                            <div class=" form-group "><label for="user_broken4" class="optional">&nbsp;&nbsp;&nbsp;&nbsp;I am broken4</label>

<input type="hidden" name="user_broken4" value="0"><input type="checkbox" name="user_broken4" id="user_broken4" value="1" class="form-control hoverToolTip"></div> 
                        </div>
                </div>
            </div>
        </div>
    </div>

Expected results:

• All checkboxes displayed on the left hand side, followed by label on the right

Actual results:

• 2 checkboxes working as expected
• 2 broken checkboxes display with the Label above checkbox and the Checkbox centered in the middle of a text box