PlaceOrder using service KuCoin returns "Object reference not set to an instance of an object"

[d2ro]

I'm trying to place a sell order on the KuCoin exchange using BtcTransmuter. Placing the order fails, but the error message in the logs does not tell us why. It seems to throw another error instead.

info: BtcTransmuter.Services.ActionDispatcher[0]
PlaceOrder for recipe <redacted> was not executed because [Could not place order because Object reference not set to an instance of an object.. Order details: <redacted>]

Does anyone have an idea?