There seems to be a number of actions that will fail to update the used volume of both inventories when something is moved between them.

I only know one for now but there may be more:

• having an item merge into a multi slot on transfer
  1. example: put orange hull in your inventory
  2. put orange hull wedge in a chest
  3. transfer orange hull to the chest, or the wedge to your inventory so it would merge into a multi slot
  4. capacity used doesn't update on either side