When you're in a crouching position and try to break a block that's 5 blocks below you, it's not breaking, but is being replaced immediately.
To recreate:
Get into a crouching/crawling❓ position
If you're at, let's say, y=70, try to break a block located at y=65.
Thank you for your report!
However, we are already tracking this issue, and this report is a Duplicate of MC-183309, which is a report that has not been resolved yet.
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