Yeah, this is an extension of the same-letter bug. If you look carefully, you’ll notice that when this happens, the letter that the items display in the pouring submenu are not the same as the letters shown in the actual inventory screen. In my experience, the letters in the inventory screen are the correct ones, while the pouring screen is usually full of malicious lies.
Providing no duplicate exists in the inventory screen (which may require manual intervention), you should be able to ignore the lies the pouring screen tells you, and pour your beverages correctly. Unfortunately, the containers really like to re-assign themselves to letters already in use after pouring operations are performed on them, especially when you attempt to repeat a crafting operation.
The really bad part of this, of course, is neither the fact that the pouring screen lies to you, nor the fact that the inventory letters get doubly-assigned (two separate bugs, you’ll note). No, the really bad part of this is the invisible nether demons which lurk unseen around you, and will immediately consume any liquid you fail to either bottle or dispose of on your first try. If answering ‘no’ to ‘pour on ground’ simply took you back to the pouring submenu, the other two bugs would be a minor display issue, of little consequence. Since, as is, answering ‘no’ really means ‘feed the liquid to invisible demons’ instead, the issue is rather more serious.
