Mauro says:

Let’s start with the
Let’s start with the Arensburg case.
Arensburg is a town on the Baltic island of Oesel: the place is now called Kuressaare and the island Saaremaa. It belongs to Estonia now but at the time of the event it belonged to the Russian Empire (it was annexed from Sweden by treaty in 1721, hence the Germanic names).
The focus of the case seemed to be the Buxhoewden family chapel and the story goes like this.
On June 22 1844 a woman had come to the churchyard to pay her respects to the family grave and tethered her horse near the aforementioned chapel. The horse shrieked and fell convulsing to the ground, before a veterinarian arrived to scene and managed to restore the horse by bleeding.
The next Sunday many persons arrived to attend a religious service for their dead. Again the tethered horses were shocked out of their wits by some unseen force, though this time no veterinarian help was needed.
The following Sunday it was even worse: eleven horses needed veterinarian attentions but four of them did not manage to survive.
Local people complained to the ecclesiastic authorities, who decided to ignore the matter, blaming the horses’ problems on some venomous plants. Churchgoers were simply advised not to tether their horses nearby.
Unfortunately "it" did not agree with the august parish council and a few days later, during a funeral service "terrible groans" were heard from the Buxhoewden chapel. Some stouter hearts called for a member of the Buxhoewden family and had the chapel doors opened. The chapel looked absolutely normal, of course, but the vault was not doing so well. The coffins had been removed from their resting place and had been heaped in a disorderly pile.
The coffins were quickly restored to their resting places. The Buxhoewden, an old Livonian military family, wanted to keep rumours to a minimum for decency sake.
The local magistrate, a Baron de Guldenstubbe, fearing that a personal enemy of the Buxhoewdens was responsible, felt compelled to open an inquiry after he personally surveyed the vault on a later date and found the coffins strewn about.
Two times he returned with others local worthies and two times the coffins had been disturbed.
As in the Chase case the Baron decided to get to the bottom of the case. He had workmen check the entire vault for signs of tunnelling, the coffins opened to check for signs of robbery, the walls sounded. Finally he had fine ashes spread in the vault and on the stairs leading downwards. The doors were sealed with both his own and the local bishop’s seals. Furthermore the local constabulary was ordered to keep a 24 hours a day watch on the chapel. After a few days the crypt was opened and, as you may expect, all the coffins had been thrown around. One had even been opened.
The Baron finally declared himself baffled and unable to solve the mystery.

The Chase family tomb is perhaps the best known istance of moving coffins.
It must be stated that the vault originally belonged to the Walrond family, who interred a single family member there, a Thomasina Goddard, in 1807, just before giving up ownership.
Two Chases were interred in 1808 and in 1812. Nothing out of the ordinary was noted in both occasions. In late 1812 Thomas Chase, the family patriarch, died and during his funeral the disturbances were observed for the first time. As in all following occasion Thomasina Goddard’s coffin had been left untouched. Other two Chases died in 1816 and again the disturbances were noted and reported to the authorities.
Since the world was now at peace after the Napoleonic hurricane, the Governor-General, Lord Combermere, decided to act.
He had the coffins relocated to their proper places and the entrance sealed. He ordered new inspections in 1819 and 1820 after noises were heard from the "accursed mausoleum": in both occasions the coffins had been disturbed and in both occasions Lord Combermere ordered them to be put in their proper place and the door sealed with his own and the family seal.
As with the Arensburg case poor Lord Combermere was driven to his wits’ ends to find out the causes. He had fine sand strewn on the floor and armed sentries posted to keep a constant vigil. Each time the "spirits" proved stringer than His Majesty Government
In the end he grew tired of the commotion in such a hallowed place and had the coffins relocated to another part of the graveyard. Case closed.

I have no explanations for the Arensburg case but a few explanations have been put forward for the Chase case.
Arthur Conan-Doyle, the great writer, a fervent Spiritualist, proposed that the disturbances were caused by the restless spirit of Dorcas Chase (buried in 1812), who was widely believed to have commited suicide. The old "oncles" (liberated slaves who enjoyed widespread respect for their wisdom and experience among both the white and the black populations) put the blame on Thomas Chase: he was an evil "massa" and he had been cursed by the countless slaves he had worked to the death. More "scientific" types put the blame on either flooding or a type of giant mushroom which could lift heavy weights before completely disintegrating. Recently it has even been alleged that the case never happened…

Mauro says:

The flooding theory seems to
The flooding theory seems to be the most popular nowadays. You can pay a visit to this website and have a look at the vault as it stands today. The author seems supportive to the flooding theory, though this has to be reconciled with both the careful investigations ordered by Lord Combmere (ie the sand would have been much disturbed) and the vault measurements, which would not leave the coffins much room to float about.
Of course there’s also the strong possibility that the case got exagerated with each retelling or that it was a downright invention, perhaps based on the fact that the coffins had to be moved somewhere else due to flooding or other problems. No trace of the fact seems to be left in the parish records, though nobody seems to have looked for traces of Viscount Combermere’s careful investigation in the Colony archive, though they are not so easy to access to the European or US researcher (ie you have to get there, easy but not cheap, and arrange for quite a few days of research in a dusty archive… while in the Caribbean! ).

"Massa" of course means a slaveowner. Thomas Chase owned lots of land and his family was very, very wealthy. He was also a colonel in the Colony’s militia. Envy and personal enemies could be the origin of some these rumour and remember that the militia’s first and foremost duty was to put down slave uprisings. A member of the Chase family was actually killed during Bussa’s rebellion in 1816 and buried in the "accursed" vault. They were surely not beloved by the slave population.

Some Spiritualists put forward the fascinating yet unproveable theory that Thomasina Goddard’s vengeful spirit was to blame: she resented being sold to strangers as a piece of furniture in an old house.
Make your own conclusions and if you happen to be in sunny Barbados remember to pay a visit!

Mauro says:

You can find the whole case
You can find the whole case in Brad Steiger’s brilliant little book Strange Guests. It has been reprinted in paperback by Anomalist Books in 2006 and is sold by Amazon. A suggestion: do not start reading it in the evening if the next day you need to get up early. Believe the facts or not Steiger is a gifted writer and you won’t put down the booh at a reasonable hour…