Not the same, but I had that as well. For me that was somehow caused by another platform that was set to provide to platforms, but which for some reason didn't send anything (might have been requesting some items as well, unsure if that was what was blocking things). I toggled the provide option off ...

Didn't manage to reproduce it like that. I did see that at one point it started the building animation, launched the items to another platform, and cancelled the building animation. But that still didn't cause the bug. So it might have been a fluke that it happened right as I did that before.

When this happened I did notice a potential trigger, but I need to try to reproduce to be sure it wasn't just coincidence. The platform was set to export to other platforms, and I was moving the cargo bays. So I had a ghost cargo bay, removed an existing cargo bay thinking it would build it in the ...

Right, forgot about the save. Here it is. I had unfortunately already fixed the exact scenario I had before (with the inserts and belts) by requesting manually, but now I have another small platform with with the same bug. Another ghost that isn't being requested. This time a cargo bay. Named that ...

Just updated to 2.1.7, no mods active (had rate calculator but disabled it as it's not updated.

What did you do?
I was building two new platforms, using both material sent from Nauvis and using material from other platforms nearby with excess stuff.

What happened?
A small amount of the ghosts ...