The bug
Saddled horses can infinitely retain Levitation effect, though particles are not shown. This is fixed by a relog.
To reproduce
Summon a tamed horse and saddle it.
Wait for a shulker to hit it with a shulker bullet.
Do
/kill.Ride the horse immediately.
Observed result
The horse will continue to behave as if it were still under the Levitation effect, even after the effect visually runs out.
Confirmed.