This is not exclusive to the new experiment. This happens regardless of whether the experiment is on or off.
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With the setup like above, placing the minecarts on the top of the hill, letting them roll down, makes the minecarts clip through the block on the right. This can make the minecart go completely through the block if more are added to the hill.
isXander
Thank you for your report!
We're tracking this issue in MC-275276, so this ticket is being resolved and linked as a duplicate.
If you would like to add a vote and any extra information to the main ticket it would be appreciated.
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