After doing some grinding to get money for Edgars new tools in the WoR, I came back to the castle to find it quaking. However, nobody in the castle comments on it, and attempting to travel doesn't take me to the ancient castle.
For reference, I went to recruit Setzer, grinded up 30k and bought the Defibrilator, and it was only when I went back to the castle with enough money to buy Flash that I found it shaking. Is that a bug? Does it mean anything?