From the looks of that picture, it appears that your sizing die was not set all the way down. When you set it, did you have your press ram up at its highest point, screw thed die down until it contacts the ram (with shellholder), then lower the ram and screw down an additional 1/4 turn. This causes the ram to 'cam over' against the die ensuring the entire case gets sized.
If you did as above, it is possible that the die is not machined correctly. Is this the first batch of cases you reloaded with this die?