Also, lets keep this in mind, per the UO Wiki:
The following items will be deleted during house collapse
So I have my doubts that these ummovable items were merely just Heavy items stuck in boxes, but perhaps maybe more of what another poster described below:
The following items will be deleted during house collapse
- Account Bound Items
- House Only Items
- Commodity Deeds
- Stackable Items
- Goza Mats
- Bank checks
- Heavy items – this applies to items that weigh 255+ stones that are immovable by players
- Linked attendants
- Vet Rewards
- Water Barrels, tubs, and water containers that weigh 255+ stones
So I have my doubts that these ummovable items were merely just Heavy items stuck in boxes, but perhaps maybe more of what another poster described below:
On a RunUO server when you place an item with a GM command in the world, it places GM-locked down. Can't pick it up, can't move it, and if you move the item to your pack with a command.. you cannot move it in your pack either. That's what's happening here and why the items are being deleted that can't be moved in the pack. Things like lamp posts, lanterns, 2 story statues, etc. were spawned in boxes and are similar, but the pedestal we're talking about here was obviously placed by a GM, EM, or seer - someone with admin capabilities to add items to the world. I would suspect that it was not a seer blessed house. Seers and IGMs blessed houses that were community fixtures and well known to the general public (at the time) - that castle was definitely not.