Walking onto any block that is 15 "pixel"s high (e.g. path and soul sand) from a non-full block (slabs, stairs, snow etc) at the causes the player to be blocked from keeping walking forward. If the player runs they can get through but slowly, and stopping causes them to be pushed backwards.
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Thank you for your report!
We're actually already tracking this issue in MC-166386, 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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