Changing a dragon's size from Medium to Large seems to be making its bite attack disappear from the character sheet (it's still Equipped in the Inventory, however).
Large size also coincides with when a a dragon gets a tailslap. The tailslap never appears on the character sheet, but it's also equipped in the inventory.
The failure of the bite and tailslap to appear on the character sheet can occur from differences in age categories or using the Giant or Young templates. The missing natural attacks also seem to affect dragons of sizes larger than Large.
A data fix is being enacted for the natural weapons.
This was fixed as part of Revision: 22419