The country was invaded on a fairly regular basis and several invaders took pains to remove to England or simply destroy the genealogical records kept. There were other times of great distress when records simply were not kept.
Both Edward I and Oliver Comwell carried off records to England - when the Cromwell lootings were returned the ship carrying them was "conveniently" lost at sea off the Yorkshire coast. I imagine the timber of the sealed hogshead has wel and truly rotted by now.
The Lyon Court burned down on another occasion.
Families were invited to re-matriculate their coats of arms but many did not bother to do so.
I am not referring to notes or references so this is sparse in detail and dates ut no doubt the information is available in detail on the web to be researched correctly.