Can't summon veno pets in Secret Passage

so...... not being able to summon a pet in specific areas of Secret Passage isn't a 'bug'? in the room with Silver frost on the left side is an area where there are no mobs - great place to lure Silver Frost to kill him - I could only summon my pet at the very front of the room where another mobs spawns but was out of range of Dismal Shade and his adds. Difficult but do-able!