Bidding is opened by W, no interference from N/S. Bidding goes:
1S - 2H
2S - 3C
3H - 4D
At this point S queries the meaning of 4D. W says it is "probably looking for no trumps".
E says, no, I'm just repeating my suit. E had placed 2H but thought they were bidding 2D.
Director is called. E wants to "just play in 4D" but director rules that W must bid as the information about the unintended call is unauthorised and 4D is forcing in almost any system.
W bids 4S. E is void in Spades and contract goes down awarding N/S 100%.
Reasonable outcome? It's troubling as E made an innocent mistake and in some ways the ruling seems harsh - yet you could also argue that it is mild especially since 4H rather than 4S is the logical bid for a weakish hand (the heart fit is 3-2).
What if E now bids 5D (they did not) - which is actually a reasonable contract?