By default, placements of a custom block allow for “fast bridging”: successive placements in a single direction by continually holding the Use Item input. Unfortunately, this feature breaks when providing an item override for a custom block.

In general, custom blocks do not need an item override. However, item overrides are necessary in a few different circumstances:

• The player-facing display name of the block and item should differ.

• An icon should be given for a block.

• A block should act as fuel in furnaces (frequently seen with wood-associated blocks).

• Item tags should be specified for usage in other systems, such as recipes. Block tags are not inherited by an item for such unless an item override is present.

Demonstration

The following video shows what happens when a custom block does not have an item override:

The Use Item action is being continually held in the video. Successive placements work as expected.

On the other hand, a custom block that has an item override issues placements haphazardly:

Again, the Use Item action is being continually held in the video.

Reproduction

This issue can be reproduced by creating a simple item override for any custom block, such as with the following:

{
	"format_version": "1.26.0",
	"minecraft:item": {
		"description": {"identifier": "bug_placement:custom_block_with_manually_defined_item"},
		
		"components": {
			"minecraft:display_name": {
				"value": "tile.bug_placement:custom_block_with_manually_defined_item.name"
			},
			
			"minecraft:block_placer": {
				"block": "bug_placement:custom_block_with_manually_defined_item",
				"replace_block_item": true
			}
		}
	}
}

This example is taken from the behavior pack in the following world attached for convenience:

This world can be opened (in Minecraft Preview) for inspection or unzipped to access the code associated with such. Also included is the above example wherein a custom block with no item override works as expected.