Steps to reproduce the issue

Create new form fields for custom article options, e.g. /templates/t3_bs3_blank/etc/extrafields/myfields.xml

In myfields.xml, create a repeating group to appear in a modal. Example:-

<field name="list_subtitles" type="Repeatable" icon="list" description="TPL_GROUP_EXTRA_FIELDS_SUBTITLES_DESC" label="TPL_GROUP_EXTRA_FIELDS_SUBTITLES_LABEL" default="{'subtitlelanguage':['']}"> <fields name="params"> <fieldset hidden="true" name="list_subtitles" repeat="true"> <field name="subslang" multiple="false" type="list" label="TPL_GROUP_EXTRA_FIELDS_SUBTITLES_SUBTITLE_TITLE" description="TPL_GROUP_EXTRA_FIELDS_SUBTITLES_SUBTITLE_DESC" filter="unset"> <option value="1">English</option> <option value="2">Spanish</option> <option value="3">German</option> </field> <field name="subssrc" type="url" showon="subslang:2" label="TPL_GROUP_EXTRA_FIELDS_SUBTITLES_SUBTITLE_FILE" description="TPL_GROUP_EXTRA_FIELDS_SUBTITLES_SUBTITLE_FILE_DESC" filter="unset" /> </fieldset> </fields> </field>

Expected result

Click the 'Select' field to display the modal. In the modal, initially there should be only the select list showing - the text field should not appear until the select option value '2' has been selected.

Actual result

However, the text field is displayed at all times. The showon function works as expected outside of a modal, however. E.g:-

<fieldset hidden="true" name="list_subtitles" repeat="true">
    <field name="subslang" multiple="false" type="list" label="TPL_GROUP_EXTRA_FIELDS_SUBTITLES_SUBTITLE_TITLE" description="TPL_GROUP_EXTRA_FIELDS_SUBTITLES_SUBTITLE_DESC" filter="unset">        
        <option value="1">English</option>
        <option value="2">Spanish</option>
        <option value="3">German</option>
    </field>
    <field name="subssrc" type="url" showon="subslang:2" label="TPL_GROUP_EXTRA_FIELDS_SUBTITLES_SUBTITLE_FILE" description="TPL_GROUP_EXTRA_FIELDS_SUBTITLES_SUBTITLE_FILE_DESC" filter="unset" />         
</fieldset>

However, this removes the repeatable nature I desire.

System information (as much as possible)

Joomla 3.5.1

Additional comments