Luzie, the key slot is longer than the pads, but so it is in the spectrum pcb...
Most divides I've seen use a key in pin 5 that is a kind of a nail/cilindre going up-down in the edge connector. They are a little bit back from the front side of the connector, allowing to introduce it further.. Could this be the cause?
In any case, Luzie's idea could be a workaround for your issue.
Does this happen as well when you plug another interface? (like the dandanator v1)