K8090 150Hz not blocked

I am sending a 150Hz signal to Velleman K8090 relay 6.

The signal appears as follows: https://imgur.com/oIWUBCY

When the relay is open, I am getting the following signal : https://imgur.com/CqEbr5s

My suspicion is that the capacitor is connected across the relay to prevent sparking but I can’t find a layout file or schematic on the website. I’d rather not go messing with the board, especially as I don’t have a hot air gun. Does anyone know why the signal is being passed through when the relay is open?

You can find the schematic on this link at page 10