Cannot enter the tugboat; can still enter the cargo and tanker ships.

Did you try the Shift-Enter command. Post a screenshot of what situation you cannot enter in, please.

Yes, the Shift Enter no longer works since the latest update. I will add that I have a huge list of mods, but can no longer enter that boat. Can enter the other ships using Shift-Enter.
https://steamcommunity.com/sharedfiles/filedetails/?id=2915307662

Okay, that's weird. It still works in my test save. If you post the save file I can look at it.

Sure, but be warned it is a large file!
https://drive.google.com/file/d/1nYo22-X_d_Y9SL3BEP8mrB1ky4-qlYNj/view?usp=share_link

That's not a Boat. It's an AI Boat. AI Boats aren't properly registered with the ship-entering logic. Crafting it back into a non-AI Boat makes the controls work fine.

AI boats also break the pathfinder, so they drive in straight lines without avoid collisions with entities (like signal buoys) or terrain. I should probably do something to disallow the creation of AI boats altogether, as I don't consider them to be useful.

Oh, that makes sense. It must have become an AI boat with the update. Thanks for the help finding this out. :)

I have no idea how it would become an AI boat all by itself! If anything that could be part of an AAI update not Cargo Ships. But happy to help.