You are measuring leakage through the capacitor of the snubber. This voltage will drop to almost zero with a load attached.
Another way to use the snubber is to put it across the load instead of across the relay contact.
Snubber circuits are available from the big resellers. eBay, Ali, Amazon etc.
They usually have a 100n/630V cap, a 220Ohm resistor and a varistor fitted.
Leo..