Was this sign similarly vandalised ? It's at the other end of the bay.
https://maps.app.goo.gl/5XjqfUwUyYANWBD47
Ah, I just checked today and it is visible and not vandalised. So strange as every other sign on the street is.
I'm guessing this could just be a case of paying up?
I there had been only the one sign, then you would have had a case, albeit not very strong, but the presence of the unvandalised sign counts against you because having seen the vandalised one, you should have looked to see if there was another sign for the bay which gave all the info. So yes, I think you would be better paying the discount, but that doesn't mean you should not submit an informal challenge to the PCN. Why not just submit some reps pointing out that the sign is vandalised and you were therefore unsure what it meant.