the bug:

when an item entity is partially stuck inside a wall of blocks, it will not get repelled out of the wall like what you'd expect, but glitch around in the wall instead.

how to reproduce:

1. create a test world and build the test contraption in image 1. the player should be facing north, or toward negative z

2. paste those commands in the command block

/summon minecraft:item ~ ~-1 ~0.4 {Item:{id:"minecraft:glass",Count:1b}}

/summon minecraft:item ~ ~-1 ~0.623 {Item:{id:"minecraft:glass",Count:1b}}

/summon minecraft:item ~ ~-1 ~0.624 {Item:{id:"minecraft:glass",Count:1b}}

/summon minecraft:item ~ ~-1 ~0.625 {Item:{id:"minecraft:glass",Count:1b}}

3. stand a few blocks away from the contraption, and break and replace the Redstone block to activate the command blocks.

4. the first item gets repelled out of the block wall, the second and third glitch around inside the wall without getting repelled outwards, and the last just drops down directly. (video in the attachment file)