Falling while wearing soul speed will change FOV and grant a speed increase.

Steps to reproduce:

1. wear boots with soul speed
2. stand on any block that shouldn't affect the enchantment e.g. grass
3. jump
4. watch your FOV rapidly change

Looking at the soul_speed.json file, this could have something to do with the enchantment_active_check condition. It's plausible that this condition incorrectly becomes true which would make the "is_on_ground": false check later on to also pass.