When i click on option in optgroup, all option in other optgroup are selected too:
<select id="ressource_regions_region_id" multiple>
<optgroup label="one-three">
<option>One</option>
<option>two</option>
<option>three</option>
</optgroup>
<optgroup label="four-six">
<option>four</option>
<option>five</option>
<option>six</option>
</optgroup>
<optgroup label="seven-nine">
<option>sevent</option>
<option>eight</option>
<option>nine</option>
</optgroup>
</select>
In js:
$('#ressource_regions_region_id').selectpicker();
Like this: bug bootstrap-select
Try adding value for options..
<optgroup label="one-three">
<option value="One">One</option>
<option value="two">two</option>
<option value="three">three</option>
</optgroup>