The original poster said that he hit it and it eventually started working again, which doesn't seem ideal.
Maybe not ideal, but better than a nonworking relay. When the relay contacts are stuck together because of only a bit of micro-welding, a mechanical shock has a chance to unstick them. But of course, that's not a fix for the missing contact protection, so…
[...] Is the Relay Expansion faulty?
Probably not - it's just that relay contacts can't just switch any load, even when nominal voltage and current seem in range.
If the load is not purely resistive (few are), there are always current and voltage spikes you need to take care of to protect the relay contacts. And because the needed measures depend on what you connect (AC or DC - see my attempt to explain it in that lengthy thread referenced above), that can't be part of a generic relay expansion.
If the relay specs are far above your actual load, you usually get away without any protection. But a pump for a pond sounds more like it could be near the specs, so there's probably no wide margin left for the contacts to "swallow" spikes without damage.