When you full length size a case and squeeze it back down to size on the body the material has to go somewhere. Since the die body wont let it expand and the ram is blocking it going down the shoulder flows up. maybe only .001-.002 but enough to cause problems if not held down.
You appear to be very close to where you need to be on the shoulder now. If the die isn't in hard contact with the shell holder you might try turning it in another 1/8 -1/4 turn. If it is in hard contact then you may have to remove some from shell holder or bottom of die.
An easy way to do this is lay a piece of 220-240 grit emery paper on a flat surface and start working in a figure 8 pattern. a little light oil helps it to cut. Measure shell holder before starting and make note of this. Work on paper for 4-5 mins then clean and check progress. Either die or shell holder works but doing shell holder makes a dedicated shell holder, doing the bottom of the die allows most shell holders to work with it.
If you have another 308 size shell holder ( 243, 22-250, 308, 30-06, 45 acp) try it there are differences in them