Crash happens while bottom player attempts to ride the 3rd entity

Summary:

crash happens while bottom player attempts to ride the 3rd entity

Steps to Reproduce:

1. apply addon in Minecraft world
2. summon a rider(such as zombie) for yourself or let a player riding on you
3. summon a rider(such as zombie) for the rider on you 
4. right click or long press on 3rd entity

Observed Results:
game crash

Expected Results:
riding sequence should swap correctly,
before B on A, C on B
after C on B, A on C

Notes:
here is a video link

https://cdn.discordapp.com/attachments/332971439554691077/1159844613545275402/RPReplay_Final1696597645.MP4?ex=65328078&is=65200b78&hm=60f95550ff5ef81e05f36037f38b10bc433d2d9d63e0e9ec284cd788f5a48958&