Do you clean your cases before sizing? If you don't, your die's will get dirty quickly. Powder and carbon residue is hard enough to score dies deeplyand can cause cases to stick.
Clean your cases first, clean your die's periodically. For really dirty dies, put a small bore brush on a length of sectional cleaning rod. Wrap some 000 steel wool around the brush, put the rod in a lowrpm drill (cordless), use oil and polish the die. De-grease die, inspect it for deep scores.