Falling while wearing soul speed will change FOV and grant a speed increase.
Steps to reproduce:
wear boots with soul speed
stand on any block that shouldn't affect the enchantment e.g. grass
jump
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.
Linked issues
Comments

Thank you for your report!
We're actually already tracking this issue in MC-271422, so this ticket is being resolved and linked as a duplicate.
If you would like to add a vote or any additional information to the main ticket it would be appreciated.
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