The bug
Pressing shift to exit a boat right as the boat is moving into a block causes the boat to clip into the block and the player to get stuck in an infinite loop of falling which the only way of escaping is to break the boat.
To reproduce
Enter a boat
Begin moving at full speed towards a solid block
Exit the boat as it connects with the block
→ ❌ The above issue happens
I'm unable to reproduce this issue in 1.17.1 and 21w42a.
[media]In the video you've provided of this problem, you appear to be playing on a third-party server. May I ask whether this issue occurs outside of this environment (in a singleplayer world) and if the server you were playing on was running any modified server software (paper, spigot, bukkit, etc...)? If so, could you please provide an extra video of this behavior whilst the F3 debug screen is enabled? Thanks 🙂