If you place a Minecart directly on top of a Slime block, the shadow of the minecart will cause the top texture of the slime to be transparent and show what's behind it without the slime texture obscuring it. See the screenshots attached.
You can see this occurring in this video here as well at 8:10: https://www.twitch.tv/videos/495712598?t=00h08m10s
Thank you for your report!
We're actually already tracking this issue in MC-162338, so I resolved and linked this ticket as a duplicate.
If you would like to add a vote and any extra information to the main ticket it would be appreciated.
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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