when you destroy sand there would be invisible floating sand that blocks you from walking and you can stand on it and if you place a block under it that block will become sand

Thank you for your report!
We're actually already tracking this issue in MC-156852, so I resolved and linked this ticket as a duplicate.

However, that ticket has already been resolved. Depending on the resolution, that can mean that it either will be fixed in the next version, or that it is not considered a bug and won't be fixed.

If you haven't already, you might like to make use of the search feature in the future to see if the issue has already been reported.

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