In a nice bit of synchronicity i read this thread when it was current and thought no more about it until i came across an account just recently in my bedtime read of the moment-Poltergeist, Tales of the Supernatural by Harry Price, published in 1945 as Poltergeist over England.
In the book he gives details:
'The vault (100 feet above sea level and dug out of the living rock to the extent of two feet, belonging to the Chase family)..made of stone, was sealed with a huge slab of Devonshire blue marble, which required four men to move, cemented into the opening...Apparently there was no disturbance until a suicide was buried there...The coffins were found disturbed on the following dates: August 9, 1812; September 15, 1816; November 17, 1816; July 7 1819; and April 18, 1820. After the July, 1819 disturbance, Lord Combermere (Governor of the island) decided
to make a test. The coffins were restored to their proper positions, a plan made of them, and fine white sand sprinkled all over the floor of the vault. Then the heavy slab of marble was cemented by masons into the aperture and Lord Combermere and others impressed their official and personal seals into the soft cement... On April 18, 1820, a noise was heard coming from the interior of the vault. Lord Combermere and the other original witnesses were at once informed and it was decided to open the vault immediately. Thousands of people gathered for the opening. All seals and cementing were found intact and undisturbed and 'not a blade of grass round the vault had been touched'...The six coffins were found to have been moved from thier proper positions and thrown all over the vault. The heaviest one (that required the strength of seven or eight men to handle), was standing on its head and the smallest one had been hurled across the vault, making a dent in the wall. The fine sand bore no imprints or other markings, but was perfectly smooth and even, exactly as it was when the vault was sealed. There was no trace of water or of anything that could have moved the coffins normally....All the coffins were then removed from the vault and buried in separate graves.'
Apparently there is (or was) another case of this which paralled these events even down to the same dates, although this second case happened in 1844, as recorded by Baron de Guldenstrubbe, (and reported by Robert Dale Owen in Footfalls on the Boundary of another world, London 1861, p186). This happened in the vault of the chapel of the Buxhoewden family in the public cemetary of the town of Arensburg on the Russian island of Oesel.
He (Harry Price does say he doesn't think this is just a story transplanted although he doesnt say why.
Just a wonder but it would be interesting to read about the flooding theory, as all six coffins (except one) were made of lead and were placed in three rows of two tiers. When the vault was opened the coffins were found displaced in such a way as to not immediately suggest it was down to just a bit of flooding.