Hello, I have a hearthstone II stove, with regular stove pipe inside the house and insulated security ss insulated pipe on the exterior topped with a cap and bird screen. Today I noticed after just feeding the stove that a couple of the joints were seeping smoke. It was a small percentage of the smoke coming out the top of the stack. The stove had been burning for over a day but the temperature just dropped ten degrees when I saw it seeping out. This type of pipe is just twist lock with no fasteners. Any ideas why it started it and if I should be concerned?