When dismounting a minecart it always is clipping me down a block I am assuming if there is only one block under the minecart. So I am always falling out of my railroads.
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Thank you for your report!
We're actually already tracking this issue in MC-148869, 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.
I have been experiencing this, too, as of the last couple of days. Upon exiting the cart (pressing shift), I am forced into the crawling position under the cart. If the block beneath the cart has open space below it, I am forced into that space.