When vines spread in a one block area underneath leaf blocks, there is a chance of an invisible block being created next to it. This block has the hitbox of a normal sized block, but doesn't show anything. If any blocks nearby are broken, the invisible block will disappear. Pick blocking on it does reveal that it is a vine. This most likely relates to MCPE-29111, however you cannot place the invisible vine directly. When the block on top is not a leaf block, the vine will spread under the bottom of that block, but only when the area is one block high.

Steps to Reproduce

1. Create a one block area for vines to spread. (where the top is leaf blocks)
2. Place a block in the middle and a vine on the side of it.
3. Set the random tick speed to a higher number
4. Observe that occasionally an invisible vine will be created

Expected Result

Either this invisible block would not be created, or it would display a vine on the underside of the leaf blocks.