An excessive amount of cornmeal on the peel will create problems as described as will an excessive amount of any kind of dusting flour. It might have something to do with the way you are opening/handling the dough. I always use plenty of flour when opening the dough into a pizza skin, but then I pick it up and give it a toss or two, if you elect not to toss it, try brushing the excess flour off of one side then flip the dough piece over and brush off the other side, with that done, immediately place the pizza skin onto a lightly dusted peel (my personal favorite peel dust is made from equal parts of semolina flour, regular flour and fine cornmeal. Once you have the skin on the peel, give it a few shakes to ensure it is free from the peel, now dress the skin and take it directly to the oven, in some cases I've been known to give the peel a couple shakes while I'm dressing the skin just to make sure it is not adhering to the peel. I have both wood and metal peels and of all my peels, the wood ones work best as a prep peel. The solid aluminum peels are best relegated to use an an oven peel. A good wood prep peel is, in my opinion, worth its weight in gold. There have been a number of excellent discussions on the use and making of wood peel here.
Tom Lehmann/The Dough Doctor