Basically, the idea here is that you did everything you reasonably could have to hold a valid ticket, but were thwarted by something out of your control.
For example:
The Transport (Ticketing) Regulations 2006 (Sr No 86 of 2006) - Reg 12, provides various statutory defences in relation to travel. The key one here is that, if you took all reasonable steps that were available to you to purchase a ticket for the whole of the travel and on completion of the travel, without delay took all reasonable steps that would have been available – but for the intervention of the Authorised Officer — to carry out any additional actions necessary for this ticket to be made valid for the whole of the travel, then you have a defence.
Let's break that down:
Scenario 1:
So you see in this scenario - you have really taken all reasonable steps to make sure you pay for the fare, and you would have except the Authorised Officers actually stop you from doing that.
Scenario 2:
In this scenario you have tried to touch on, but the environment makes it impossible to tell if it worked or not. Many older myki readers are also defective. When you get to your destination, you should be permitted - under the regulations - to make good your fare ie. you took all reasonable steps that were available to you to purchase a ticket for the whole of the travel and on completion of the travel, without delay took all reasonable steps that would have been available to carry out any additional actions necessary for this ticket to be made valid for the whole of the travel.
Got it?