I know others have pointed out this bug but the highest ones don't seem to explain exactly what is happening. This is most likely an issue with the new soul speed enchantment, as it occurs only on blocks as tall as soul sand, and no other height of block will cause the bug to occur. When standing on a soul sand or path block near a drop the player will move towards the drop, and player movement is slowed if you fight the push, also this bug will occur even if you don't have the soul speed enchantment. This is not the most problematic issue but it is very frustrating in soul sand valleys and villages. If I find any more info on this bug I will attempt to update this post.