
Hey! Typically if they are stored on their side/upside down, the oil can leak out. Also if they are heated to hot/to quickly, the oil will start to bubble up through the mouthpiece. Assuming you store it vertical and not upside down, you can typically clear a blockage by A. Letting the cart sit vertical and preheating it (not on the maximum heat setting) B. (Sounds crazy) but if you sit on it for like 5 mins, the oil can sometimes warm up enough to fall back into the bottom of the heating coil
If there isnโt a button on it, you probably cannot preheat it. I would recommend sitting on it or warming it between your hands. Maybe even warm water, but you have to be careful of the electronics and such. I use a cart like this (see pic), so it can be easily detached and cleaned if needed. Plus the batteries are more customizable. Mine detaches from a main battery and has 8 different temperatures