Blocks with repeaters don't collapse

Perch 3 has collapsing Blocks, but they do not collapse if there is a Repeater inside the Block. Eg template:

<!--*IMAGE WITH CAPTION*-->
        <perch:block type="image_plus_caption" label="Image with Caption">
            <div class="row">
                <perch:repeater id="image_with_cap" label="Item">
                    <div class="col-md-4 inline-item feature-box text-center">
                        <p><img class="img-responsive" src="<perch:content type="image" id="image" label="Image" width="720" height="480" crop="true" order="2" />" alt="<perch:content type="text" id="alt" label="Image Description" order="3" />" /></p>
                        <perch:content id="text" type="textarea" label="Text" html="true" editor="redactor" imagewidth="750" imageheight="500" size="xs" />
                    </div>
                </perch:repeater>
            </div>
        </perch:block>

 Perch Runway is up to date
 PHP 5.6.28 is up to date
 MySQL 5.6.34 is up to date
 Image processing available
Summary information

Perch Runway: 3.0.11, PHP: 5.6.28, MySQL: mysqlnd 5.0.11-dev - 20120503 - $Id: 76b08b24596e12d4553bd41fc93cccd5bac2fe7a $, with PDO
Server OS: Darwin, cgi-fcgi
Installed apps: content (3.0.11), assets (3.0.11), categories (3.0.11)
App runtimes: <?php $apps_list = [ ];
PERCH_LOGINPATH: /perch
PERCH_PATH: /Users/simonclay/Dropbox/Clients/Lighthouse/Lighthouse Website/perch
PERCH_CORE: /Users/simonclay/Dropbox/Clients/Lighthouse/Lighthouse Website/perch/core
PERCH_RESFILEPATH: /Users/simonclay/Dropbox/Clients/Lighthouse/Lighthouse Website/perch/resources
Image manipulation: GD
PHP limits: Max upload 32M, Max POST 32M, Memory: 128M, Total max file upload: 32M
F1: 3b606135b33e6a102526838f4152a807
Resource folder writeable: Yes
SCRIPT_NAME: /perch/core/settings/diagnostics/index.php
REQUEST_URI: /perch/core/settings/diagnostics/
DOCUMENT_ROOT: /Users/simonclay/Dropbox/Clients/Lighthouse/Lighthouse Website
HTTP_HOST: lighthouse:8888