This does not apply to all calculated columns, just to some of them J.
Here is an example: I’ve had created a calculated column with the following calculated value [ID], initially the column gets populated with the item ID just fine.
After the item gets updated, the calculated value disappears from the field. Here is a little workaround I’ve came up with.
Create a workflow in the SharePoint Designer attach it to your list, workflow should start on item creation, allow this workflow to populate the field with the desired value.