I have a rather old RCBS loading block that holds 80 cases. When charging, I never put more than 40 in the bottom half of the block. When I charge the case I start from the top left had portion at the middle of the block, and move the charged case to the top left hand corner of the top of the block. Always keeping an empty space between my charged and uncharged cases, When I have all 40 charged, I visually inspect them, one at a time, before seating the boolit. Never seated a boolit in an empty case, or a double charged case this way.
Sometimes it's all routine.