Updated description by EVGENSYPERPRO 
Summary:
Sniffers, camels, horses, donkeys and mules can enter boats when they're babies. While inside of the boat, they can grow up, leading to adult mobs in boats. As the hitbox of an adult mob is larger than that of a boat, the boat can then only be entered/broken from below.

In the java, when baby sniffers, camels, horses, donkeys and mules grow up in boats, they automatically exit the boat.

Steps to reproduce:

1. Place a boat.
2. Spawn a baby horse on top or next of it, so that it enters the boat.
3. Feed the horse with haybales.

Observed results:
The adult mob stays in the boat.

Expected results:
An adult mob will automatically exit the boat.

Original Description:
Hello to the Mojang team, there is a bug that when the sniffer child sits in the boat and you give it torchflower seed, and when it grows up, it gets stuck in the boat. Thank you.