This is not an isolated case. It is by design. A systemic injection tiny seam at the sealing point of the screw on the pot in conjunction with an albeit elastic but relatively hard plastic ring closes the tiny bead not completely. A softer plastic, this could perhaps prevent, but probably not. It "hisses" after a short time and connected so that the temperature does not decrease much more rapidly coffee gradually starting, faster even than in cans with this name. Remedy to Rotring: tangential cut sealing surface on the can or better yet, no bead. :-)
