There are potential MI and UI rulings here.
West has UI that his partner thinks he has the minors, however I don't think passing 5Cx is a LA opposite a passed partner (in fact it's arguable that 5C should be pass-or-correct by a passed hand, and then you can use 4NT as something more subtle).
North/South have MI from the initial explanation, but I can't see that affecting the auction, so unless they can explain why they are damaged I (other than 'unhappy') I would rule that the table result stands.
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This contract normally goes down one with a lead in either hearts or clubs. Depending on the auction I expect no more than about one third probability for a lead that gives the contract.
If West is declarer I would expect the contract to make much of the time. Why on earth would North pull out the ace of hearts as the opening lead? I agree the auction is relevant, but on the given auction it's far more likely that dummy has a singleton heart than partner. And I can't see any reason to lead a club (from Jxx) rather than a spade, when you know that dummy thought that 5C was a good contract opposite the minors. If West had been 1660 instead of 0661 would you suddenly suggest that a spade was obvious? And what about all those textbooks telling us it's always right to lead a trump against two-suited auctions?
I made +550 on this deal, and I didn't find the chosen spade lead surprising or particularly worthy of criticism.
Along with bluejak, I don't understand the legal basis for your split score. You say that North's 5S bid was "close to" wild and gambling, but that is not the same as ruling that it is wild or gambling. And given that 5Dx was likely to make, pulling to a contract that should have gone for 300 seems eminently sensible to me.
p.s. as a slightly off-topic diversion, a 2NT overcall of 1S to show a two-suiter including diamonds (i.e. diamonds + clubs, or diamonds + hearts) is legal. But no-one is suggesting this pair were playing it.
P P 1♠
2NT[1] 4♠ 5♣ Dbl
5♦ P P Dbl
P 5♠ Dbl P
P P
Result:
5♠ dbld -3
NS -500