it could be dragging on the lugs and that's why its 2 spots. what i would try is mark a few cases, just a sharpie on one side and load a few so that the sharpie line is always the same direction, IE towards the ejection port, single load and fire, repeat 4-5 times. seee if the burn marks are always in the same spot.
For example round loaded with line at the 3 o clock position and the burn marks are always at the 6 oclock position. Now you know its something in that area and can look around that area to find the issue.