Any clue why this happens?
https://steamhost.cn/steamcommunity_com/sharedfiles/filedetails/?id=3383930825

If I start the server with the custom boat in loading range, it looks normal, but upon walking away far enough to unload it, then walking back, this specific part is consistently invisible but can still be walked on and built on.

Clean Sweeper doesn't refresh it, just changes boat material skins like normal but with the invisible gap still present.

Edit: Apparently moving the boat forward, then walking away and coming back results in the back 15% of the boat being invisible instead, so it's definitely something to do with how the boat shape tries to render in based on its current position in the world, rather than a very specific problem shape during construction or something.

Edit2: I've discovered that walking away from the boat WITHOUT entirely unloading the tiles it is inside of somehow refreshes the parts of it that are invisible and gets them to appear. Using the Horizon Expander, you can even see the rest of the boat pop into existence without taking it off screen.
Invisible portions of a boat can be stood on but render all things built on them in that spot to also vanish and be completely uninteractable until the invisible custom boat portion returns. However, the objects built on these invisible portions still seem to exist and function, such as the nautopilot which, if its beacon is picked up, will auto-disable itself even while in this invisible/unrendered state, though without any sounds or indication.