Scenario 1.
I get on at station A. I tag on.
I pass thru station B without tagging off because I want to travel to station C. But due to trackwork and buses. Bus drops me off in the street.
I then need to tag off at station C that is closed due to trackwork. (Bus is a private contractor and no opal device).
Inconvenient! Officially I would need to walk to opal device to tag off or get charged the maximum fare.
Scenario 2.
I forget to tag on at a non gated station. I exit a gated station.
Opal says you have already tagged off from the previous journey the day before for example. Barrier gate does not open. See attendant.
Attendant has no opal card reader or way of fixing issue.