Warping entities riding entities is inconsistent

This may seem like an oddly specific bug, however it's become frustrating to me due to the nature of it. The newest update, Java Edition 1.21 introduced a feature where entities such as horses, minecarts and boats can be ridden through portals, maintaining the player in a riding state on top. This feature also finally allows entities to be warped using /tp with players riding them, which is very useful to a map-maker like me. However, one thing that I've noticed over time is that there is an inconsistency present. Attempting to warp an entity like a boat only works roughly 50% of the time, while it works 100% of the time when there is no player in it. I can not seem to find any external reason why this occurs.

This bug can be recreated simply by using the command /tp @e[type=boat] ~ ~0.5 ~2 while in a boat on water, and seeing how often the boat actually moves while a player is in it, vs. when they are not. The picture attached is a screenshot where I spammed the command above in a boat, and you can see on the far "Z" coordinate on the command how often the boat with my player in it actually successfully was teleported.