Update 4.1 | v0.8.5 (b598). And earlier.
It was at this point that I noticed the numbers didn't add up. Earlier on this same world, this bug did not appear; one of the distant docks correctly refused to take a cargo ship because I didn't have enough of them. A simple fix, just buy another. Because of that, I was under the impression this bug had been fixed- I was already aware of it, after seeing a report on GitHub from 0.8.2a (the poster didn't mention build number three months ago). However, as this image shows, taken on v0.8.5, it was not fixed.
Reproduction from a blank slate is unknown. I used to think just throwing innumerable docks down would do it, but evidently not. Instead, world attached, and I will note that the proper behavior of "insufficient cargo ship" happened at a time when none of them had modules attached to their docks- and the current issue has arisen when all (or most) have jobs assigned: 2 harvesting from World Mines (oil and coal), the other 6 with trade contracts (there's 2 ships trading gold for oil). That could easily be a factor.
So. Reproduction:
- Load up the attached world.
- Place a dock somewhere. Unity-build optional. It'll be easiest to place on the distant reclamation, where most of the ships already are; this coastline does not like docks.
- Watch a ship drive to it!
It is more obvious if you first destroy 3 docks (the 3 working the diesel-gold-crude oil loop in the distance will have no impact on the industry until/unless the current World Oil Rig runs out), or purchase 3 ships, to set active & available ship counts equal to one another.