I go in and out of JNB with Firearms (hunting) several times a year. Usually the firearms desk people are quite proficient.
It is still the "porters" that are the pain. NEVER take your eyes off them.
I once caught one carrying my guns out the door instead of bringing them to the security office for pickup. When I questions him, and the uniformed agent, all I got was, " He was taking them to the car for you".
Ya right, his car.