The point of fining people is to ensure that people pay for their parking.
If it can be shown that you paid the correct amount for parking for the duration in that location, then there is no justification for a fine for a minor, trivial, or inconsequential mistake in the process.
Yet these companies and their rules seem to make it their mission to make it hard for drivers and refuse appeals for no obvious reason.
They need to be held to some kind of standards when awarding them the contracts.
Ruling that a paper ticket is non-transferrable to a different vehicle is another one that's unjustifiable in my view, but that's a different story.