This issue appears to still be present in version 1.15.1. I'll see if I can find any specific lines of code that may cause this. Has annoyed me quite a bit with many storage systems on farms especially when a certain functionality relies on the items always making it to the bottom hopper before the chest.
I believe this is just screen tearing, which would make sense considering it's not visible in the screenshot, since it's related to the refresh rate of your monitor. Try turning on v-sync for now.
Alex Jacobs
This issue appears to still be present in version 1.15.1. I'll see if I can find any specific lines of code that may cause this. Has annoyed me quite a bit with many storage systems on farms especially when a certain functionality relies on the items always making it to the bottom hopper before the chest.