Perhaps there is some solder on the coil wires to the pins (cannot remember) but, if there are, the solders would be over the wire wound a few times over its terminal (the relay pin). This kind of solder will not fail like the solders in PC boards. Anyhow, I think relays are designed to withstand vibrations. A more common failures are due to corroded/burned pins and the respective sockets in the relay connectors.