If you look at the first screenshot, you can see a small gap at the hopper where you can look through.
Linked issues
is duplicated by 1
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Comments 13
Resolved as duplicate of MC-1794
this is not a duplicate at all, please reopen it.
MC-1794 is about small dots between blocks, this is a graphical glitch.
This ticket is about the top block being a bit to high, thus not connecting the two parts.
This is especially annoying as it is quite visible on any hopper placed at eye level.