When sprinting and jumping, slowness loses its effects as players can sprint jump at almost their normal speed.

The zoomed in vision can give the illusion that this is not the case however.

When using /effect <Name> Slow 1000 1000 you would expect the player to be completely immobile.

But they can jump and move, as well as hold down the sprint toggle to start sprinting on the spot, then proceed to jump and move as far as a normal jump-sprint would be.

Proposal: Add the slowness effect to movement in the air as well. Or disable sprint toggling from working when under the influence of the slowness effect as its impossible to sprint by double tapping when under the effect.