Invasions????

[Captain Jason]

"Known Issue:

Skeletons may sometimes fall through the terrain during Invasions.
Bonuses from Sea Charms and Navigational Charts are not being applied correctly."

They may have turned off or made invasions less common because of this.

They can normally happen at any time of the day, but you will always get the half an hour warning right on the hour, meaning the actual invasion will always come when it is something thirty, like 4:30, 6:30, and 8:30 could all be times an invasion happens.