Glad you weren't hurt.
Endoscopes an be had for less than $20. It is a camera on a cable, plugs into your phone or computer. I've thought about mounting mine on my Dillon, so I could see into the case before seating the bullet. I might just do that now. It wouldn't take much to do it.
ANY disruption of the loading sequence when using my Dillon causes me to check all cartridges in process at that moment. I will pull the next couple of cases off stage 3 and weigh the charge, for instance, if I have a primer mess up, or even if the case in stage one doesn't go up into the size die because I didn't have it aligned properly.
You can't be too careful.