Hello Klemen.
I may have found a bug not sure if its Minecraft or MCreator but Its on both 2020.1 and 2020.2 for Minecraft 1.14.4.
Console did not detect any error that I can see no warnings or critical errors highlighted like there would be normally.
I have a entity with movement controls and ridding controls enabled but only forward movement.
I have one procedure to simply test if the entity is being ridden and if true then give the entity a potion effect (the entity being ridden not the player).
The model seems to not be the issue as having no procedure seems to function fine but it moves slowly so I added some potion effects. When controls are working it works fine, but leaving the controls then ridding the entity again can randomly cause the player to not have movement controls.
This can lead to no damage being able to be done to the entity from the seat nor does holding shift kick you off the seat. Logging out of the world then logging back in will kick you off your the entity but I am not sure if its rolling the save back. The game seems to not be frozen as animations and creatures from what I could tell still work but I could be wrong.
I will provide the debug log file and the workspace in the zip below, I also have the block bench model and texture in the zip in case you need to take a look at the model its self.
I have found the problem. The bounding box is that big that it always collides with something. After I reduced the bounding box it started to work. The collision algorithm was probably not made for that big models. After I reduced boat size, it also became very fast, actually too fast :D
A side note, if you add potion effect each tick, set the duration to 1, otherwise, you will accumulate potion effect and this can crash the game.
Btw, nice model and idea, I really like it!