I put 2 potions in my hotbar next to each other, a night vision potion and a slow falling potion.
If I begin drinking one and switch to the other at the end of the animation, something weird happens. In Creative Mode, it turns the second potion into the one you were drinking at first so that both become that potion. In survival, the second potion is deleted and the first is used up as usual, becoming a bottle. You gain the effects of the first potion in either gamemode.
Thank you for your report!
We're actually already tracking this issue in MC-158705, so I resolved and linked this ticket as a duplicate.
However, that ticket has already been resolved as Fixed. The fix will arrive in the next version or is already included in the latest development version of the game.
If you haven't already, you might like to make use of the search feature in the future to see if the issue has already been reported.
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