The effect is most notable when interacting with other mods since those can vastly increase Max HP with equipment (i.e Apotheosis and Ensorcellation) and when taking those off, the current HP is apparently saved / unchanged. As a result speed can be reduced to 0 due to a very high negative modifier. The issue seems to be rather rare and can be worked around when known by just taking the Rage Gloves off but after some searching it doesn't seem to be. Hopefully you can just implement a check for Current Health being bigger than Max Health to not scale.

Steps to reproduce:

1. Equip equipment which adds Max Health (Chest plate with Vitality Enchantment from Enscorcellation, Apotheosis Modifiers and Gems)
2. Have full HP
3. Equip Rage Gloves
4. Check both kinds of Speed (normal)
5. Take off the equipment which adds Max Health
6. Check the Speeds (Reduced / 0 depending on the difference and level of the gloves 2nd ability)
7. Take off Rage Gloves
8. Check the Speeds (should have returned to normal)