In Minecraft snapshots 24w21a and 24w21b, the attribute modifier for attack speed given by the mining fatigue status effect was mistakenly minecraft:minining_fatigue (MC-272342). This typo was fixed in Minecraft 1.21 pre-release 1; however, already-existing attribute modifiers do not have the typo fixed. As a result, when the mining fatigue status effect expires or is cleared, the attribute modifier is not removed.

The attribute modifier persists until the player dies; I would expect the upgrade to correctly update the attribute modifier so that the expected behavior of mining fatigue persists across versions.

Steps to reproduce

1. In Minecraft snapshot 24w21b, give yourself the mining fatigue status effect, with an exaggerated amplifier to see the attack speed reduction: /effect give @s minecraft:mining_fatigue 30 4 false
2. Observe that when the effect ends, the attack speed returns to normal.
3. Give yourself the effect again.
4. Load the world in Minecraft 1.21 pre-release 1.
5. Observe that when the effect ends, the attack speed is still debuffed.
6. Run the following command to verify that the old attribute modifier still exists: /attribute @s minecraft:generic.attack_speed modifier value get minecraft:effect.minining_fatigue