Duplicating equipment: Just lag?

Happened twice to me since I've started playing, but when I was in my house, switched classes, and used the equipment swap, it erased the equipment on my secondary class and replaced it with the equipment on my primary. Thing is, I don't think I was really lagging at the time when this happened.
So, two questions:
1. Is this just caused by lag?
2. What should I do to get this to happen again?

We can't tell you that lol, you would have to trace your steps, and then give us updates so we can help.