Pretty self-explanatory as bug but I'll link a video on youtube that showcases what is happening: https://youtu.be/pF6TkngsCUU
When I try to feed a llama, a portion of the stack of wheat or bays I'm using is glitched and reappaers when you switch item in the same spot (or simply right click on the empty spot where there was the stack of items)
Environment
Windows 10 Pro (latest version)
Java 8 (latest version)
Using latest version of Optifine. Happens in singleplayer and multiplayer.
Dupe of MC-93825
Also, modded game (Optifine) is not supported