2 Slabs A Half Block Apart Will Be Pushed By Piston.

Thank you for your report!
However, this issue is Incomplete.

Your report does not contain enough information. As such, we're unable to understand or reproduce the problem.
Please review the guidelines linked below before making further reports.

You can also check out this video guide by @unknown about how to create good bug reports.

In case of a game crash, be sure to attach the crashlog from [minecraft/crash-reports/crash-<DATE>-client.txt|https://minecrafthopper.net/help/guides/finding-minecraft-data-folder].

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.

Quick Links:
📓 Issue Guidelines – 💬 Community Support – 📧 Customer Support – 📖 Game Wiki

I believe this is the issue that he was stating