I've tried this several times and have consistently found that when sand or another block falls it glitches upward at least once while falling or after falling and falls from its original location again or from slightly lower.
I've tried this several times and have consistently found that when sand or another block falls it glitches upward at least once while falling or after falling and falls from its original location again or from slightly lower.
Please tell us the coordinates of where the problem occurs.
Perhaps a duplicate of MC-93810