Player cannot exit boat / stuck in boat on servers

Trying to exit a boat on a server would cause you to be put too low, causing you to become stuck. The severity of this bug varies between different servers.

Steps to reproduce:
1. Go on singleplayer.
2. Enter a boat and exit it, making sure there are no blocks in front of you or near you.
Results: The game puts you on top of the boat. ✔
3. Go on multiplayer.
4. Repeat step 2.
Results: You get put too low in the boat, causing rubber banding and getting stuck. ❌
Expected results: Multiplayer having the same results as singleplayer.

Original Description:
My gf and I are playing together and she is having trouble getting into and out of boats.

I've seen some other people post issues with exiting boats, but they don't sound exactly the same.

I am hosting this server as a multiplayer server, and she is connecting from her home as a client.

When she presses SHIFT to exit a boat, she stands up and cannot move. She holds W key and taps the SPACE bar to try to jump out. On her screen, she is teleporting back into the boat before she hits the water. On my screen she is not jumping, instead she's just slowly creeping forward until she reaches the edge of the boat.

When she is near the edge of shore, she can exit the boat no problem. She just lands on the shore. But when she is away from the coast in deep water, she gets stuck standing on the boat.