Rarely the plug get stuck to the bottle and becomes hard to open. We think that this happens more often during the winter months due to the fact that the cold freezes the oil that might be around the plug. The best solution that we have found for this problem is to PLACE THE BOTTLE NECK UNDER HOT TAB WATER FOR FEW MINUTES  to warm up the oil making easier to take the plug out. To remove the plug simply pull it upward one it loosen up.