Video demonstration of this bug:
https://drive.google.com/file/d/1g2kxajFTBCD2AFpRY3ficatdeJsr6n2q/view?usp=sharing
How to reproduce bug:
Place down (any) slabs, cakes, (any) trapdoors, (any) mob head and heavy cores.
Make sure to put something that affects movement, such as Honey Blocks, Soul Sand or even Ice blocks.
Walk on them
Expected result:
walking on the blocks mentioned above would act like walking on a full block
Observed result:
movement acts like there's no block between the player and the block that changes movement
Related issues
Comments

done!
Would MC-1127 describe your issue?

Thank you for your report!
We're tracking this issue in MC-1127, so this ticket is being resolved and linked as a duplicate.
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Please add full steps to reproduce the issue, observed result and expected result. A video can help, but not replace these steps. Your report will be resolved as incomplete otherwise.