Basically, your jump is cancelled unexpectedly in this specific case.
How to reproduce this bug:
Create a superflat world and allow commands (superflat so the terrain is convenient);
Run the following commands:
/setblock 47 71 73 prismarine_slab
/setblock 47 72 75 prismarine
/setblock 47 71 75 prismarine
/tp @s 47.063848975254324 71.5 74.15667647020095 -2.2 50
Then, perform the following input, aka "rex bwmm with d" (it is not that easy):
Jump with S, walk 1t with S upon landing, jump forward with W+D and immediately release D, hold space.
The video shows how to reproduce this bug. (Sorry for the mkv format if that is inconvenient)
This bug can be consistently reproduced as long as you do the "rex bwmm with d" correctly.