Summoning in a mob with a passenger and immediately dismounting the passenger (in the same tick) produces a desync.

How to Reproduce:

Impulse Block into...

summon minecraft:chicken ~ ~1 ~ {Passengers:[{id:"minecraft:zombie"}]} 

Chain Block...

execute as @e[type=minecraft:zombie,limit=1] run ride @s dismount 

Press button and observe desync. Server thinks passenger is dismounted. Client thinks the passenger is still riding.