I do small batches on my 550. Boredom is real, and it's dangerous. I've only had two squibs with that press, but it was when I was loading for more than an hour at a time. I have a light on the press, and I load with a somewhat bulky for 9mm powder. There is no doubt that it's there or not. (I caught when I fired both squibs, no damage done)
On a single stage I break up the operations. Sizing/decapping, then later on priming. Neither operation causes squibs, so I can have the TV on while doing them. Powder and bullet seating/crimping get all of my attention. I've only loaded one squib on a single stage, but I figured it out while loading. The hard part was finding it, but they were .44s with a hefty charge, so weighing them sorted it out. The problem then was that I was in rush.
-Take your time
-If you're tired or impatient, process brass but don't load
-ALWAYS see the powder charge, even with a progressive. If you didn't see it, proceed as if it's not in there.