I am having trouble with a black line appearing at the outside edge (the edge away from the handle) of my transfer paper when I'm pressing my mugs. Funny thing is that it only happens sometimes and then only on particular designs. But when it happens, it happens on a pretty high percentage of my mugs. For instance, yesterday I pressed 6 different designs. Only 1 of them had the black line problem, but it occurred on 6 out of 12 of that design that I pressed. I guessed that it was caused by the edge of the transfer lifting somehow so I started taping along the entire edge of the transfer. That didn't seem to help. I reasoned that perhaps the edge was falling into some spot in my mug press that wasn't having the same pressure as other places so I tried putting the mugs in the other way around. That didn't help either and besides, it didn't happen with other designs that were the same size and fell into the same place in the mug press.
Any ideas?