Not sure if this is a long standing issue or if it was introduced recently. When I was playing in around in the new pre-release that if you are crouching while standing on a waterlogged slab and you press against a block it makes you jump.
Linked issues
duplicates 1
Comments 1

This is a long standing issue (MC-8959/MC-44560), actually predating waterlogging. Sneaking shouldn't be required to reproduce it.