The bug
Two of the lines on the cut copper block are not connected like it should. And it's only on one side of the block. The other sides are connected.
Linked issues
is duplicated by 7
2 more links
relates to 2
Attachments
Comments 15
It would be as simple as rotate one of the side textures to allign with the others.
Maybe mirrored. It would mean work again with some blocks, but it would be a solution.
Can confirm in 20w49a. This only affects the faces of the block that are facing north and east. Also relates to MC-158295.
Same problem with bricks, no easy way to fix it.