Not having one myself this is speculative, but I suspect ‘we’ still use state of the art 2000 (or before) transponders that are slow and do not have user-replaceable batteries 
Fees being lost? It will never fly
Plus the idea is all too reasonable!
I had the same problem as Joe1 (etag failed to read, presumably due to age of etag or more accurately age of battery in etag, got pinged with admin fee) - and RMS mailed out a new etag.
As with a lot of these things, it may depend on the specific person in the call centre that you speak to. I didn’t get the admin fee waived but they did mail out the replacement etag.
I was interested to read about this as I only ever used a toll once, some years ago, when I was travelling from outback Queensland to a Brisbane hospital for tests.
My husband attached the unit to the windscreen of my ute and when I sold my car a couple of years later I rang Queensland Transport to inform them of the sale and it was only then that they told me I should have removed the tag and transferred it on my next car.
I was never given this information when I bought the tag from a bush Post Office/General Store!
The current user interface is out of the stone age.
If I have music playing in the car at the time of going through the toll point, I can’t hear the beeps at all. So I have to remember to pause / mute the music.
If you miss the beeps then there is no way to find out what happened.
Without going down that rabbit hole, one thing is certain: The privatisation arrangements introduce additional players and make it harder to resolve problems / get to speak to the right place.
Allegedly that happens - but only if you are a frequent user. If you are an infrequent user then your etag may have been OK the previous time that you went through but flat this time.
Once I had the experience of the tag not working and received a notice with the extra charge.
I rang and said that it was not my responsibility as it was their receiver that not working as my tag had worked on the outward journey. I would not pay for the additional charge unless they sent proof that their receiver was working ok. Otherwise I had a faulty tag and so need to be replaced and so I should not be charged the administrative fee.
I was let to just pay the toll. Never received a replacement tag.
