I find myself victim of a burner with a very annoying "feature": If the tray is left open too long it closes itself.
I was burning a set of 5 disks, I walked away during the burn of #4 to deal with a problem elsewhere. When I sat back down at my computer it was burning #5.
This could happen because the target media is DVD+RW and the warn on non-blank disk is off--I'm almost always burning onto non-blank disks. The drive door closed itself, the system went happily away burning the next image.
I've done this by accident a few times in the past over the years accidentally closing the door while reaching for the disk but simply blamed myself for the stupidity, this scenario is worse because it's unavoidable other than by turning off auto-insert.