In the plural model there is an error in this.
Somewhere above $this->applySqlStates($query); in the prepareQuery function you probably have:
//WHERE - FILTER : SomeBool
if($filter_somebool = $this->getState('filter.somebool'))
{
if ($filter_somebool !== null){
$this->addWhere("a.somebool = " . (int)$filter_somebool);
}
}
that does not work, copy the prepareQuery function in a forked plural model file and change the filter for the boolean:
//WHERE - FILTER : SomeBool
if($this->getState('filter.somebool') !== null)
$this->addWhere("a.somebool = " . (int)$this->getState('filter.somebool'));
Cheers