I'm not sure about the prevalence of this issue today but about 10 years ago I helped create a fraud protection system specifically targeted at deposit return f

I'm not sure about the prevalence of this issue today but about 10 years ago I helped create a fraud protection system specifically targeted at deposit return fraud. However, at the time at least the problem apparently wasn't so much people manipulating return machines but rather bottles miraculously appearing out of nowhere from within the system (i.e. parties trying to register a bunch of bottles more than once or attempting to remove bottles in-between checkpoints in order to "reuse" them later on).