Technically not a bug, but a feature to prevent normal players from picking up objects they're not supposed to be able to pick up!

I wonder if a possible way to make this less annoying for GMs without having to have allmove enabled all the time could be to always allow them (GMs only) to pick up objects from the backpack, regardless of movable status of the item?
Also note, this method will add "base" items that only use tiledata default values for properties (exception for items listed in harditems.dfn) instead of DFN ones:
'add <itemID>
While these methods will add the item with properties defined in the DFN (if such an item has been defined in the DFNs):
'add item <itemSectionID>
'add +
<select item in menu>
In the above examples,
itemID refers to the direct hex (or decimal) ID of the item from the client, while
itemSectionID refers the the section ID/header given to the item in the UOX3 DFNs, such as
[bagofreagents] for a bag full of magical reagents, though these are often given identical headers to their actual itemIDs - such as
[0x0f7a] for a black pearl.