Sand, anvil, etc will turn into an entitiy when placed on top of shulkers, and can be stacked up to 2 blocks. Doesn't matter if the shulker positioning was sideways or straight. You can place the block by making a platform above the shulkers, to make it falls directly towards them.
If you keep placing the block for a while, it will get broken, it may fall into the shulker, or to the side of shulker.
Cleaning up old tickets: This ticket has not been updated recently (~1 year+) so is being closed as Cannot Reproduce. If you feel this is still a valid issue then please comment, or create a new ticket following the Issue Guidelines.
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