Entity's movement speed does not get updated by potion effects until the entity stops moving

Partner Rank: 1

Verification Builds: 1.16.2.0 (UAP dev build)

Regression Builds: Never worked

Summary: Entity's movement speed does not get updated by potion effects until the entity stops moving

Affects currently Live Content: Yes - Currently affects our (Spark Squared's) ZOMBIES map when using the throwing rocks to stun the enemies.

Impact: Limits ability to freeze entities in place right away, for example, using a high level of slowness

Repro Steps:

1. Spawn an entity that moves, like a creeper
2. Wait until the entity starts moving
3. Throw a slowness potion at the entity

Observed Results: Entity does not get slowed down until the entity slows down to 0 or near 0 speed

Expected Results: The entity updates its movement speed right as the effect gets applied

Screenshots/Videos attached: Yes

Notes: