The bars connecting fences are modeled differently between the item and block.
- The bars on the item are 2 pixels high, while on the block they're 3 pixels high.
- The lower bar is positioned too low on the item.
To fix the item model, the lower bar needs to be moved up 1 pixel and extended 1 pixel upwards, and the top bar extended 1 pixel downwards.
The model provided in MC-182716 also corrects this.