Mike - It seems like you have everything in place so it may be the oven with hot spots. Although, you mentioned that you use minimal flour on the peel and the bench - my suggestion would be to eliminate all flour from the peel and the bench. The standard practice for NP pizza is dipping the dough in a mound of flour until dried out, then removing all flour during the shaping of the skin, with no flour on the bench at all. Then the peel needs to be seasoned enough for no flour at all during the placement. I have a wood peel, but I know that metal peels will also perform as needed in this regard. I don't know the hydration you are using, so that will obviously factor in when trying to remove all flour from the process.
Also, if there is flour on the bottom of a pizza, even a little, there will potentially be a black ring under the pie. Cooking directly on this black ring, if left without scrubbing off with a brass brush, will definitely start to burn the bottom of the next pie if it is placed directly on it.