Haul trucks partially loads from shipyard

Issue description

Haul trucks only pick up 60 units max from the shipyard when it needs to be emptied.
My main ship arrived from the quartz mine with around 4k quartz.
It fills up the dock with 400 units.
Lots of T2 trucks and some odd haul truck comes to empty the dock.
I notice that the haul truck only pick up 60 units, even if they are the only one unloading for the moment.
I also noticed that some of the T2 trucks got a partial load when there were a few of them trying to grab cargo at the same time.
While observing this issue the dock seems to never dip from the number 400 as long as there still is cargo left in the ship.
There are also room in the receiving storage for a few k units still.
Noticed that the haul truck on the last unload managed to snag 120 units.

Expected behavior

I want the dock to be able to fill up the trucks that wants to unload, at least when there still is cargo on the ship.

Reproduction steps

Load attached save.
1 haul truck has just loaded 60 units of quartz from the dock.
If it's not enough data, slap down a big storage for wood and use the main ship to grab some wood from the sawmill.
Although the haul trucks cant move this product, the t2 trucks gets partial loads of wood. (Got one on a screenshot)
Otherwise, wait until the quartzmine is full again and send the main ship to grab a new load. If needed add a big loose storage.

Game version

v0.4.9a

Attachments

Partial Unload.save

Files not imported: Partial Unload.save

This is because the shipyard has a max capacity. Each time it gets emptied by e.g. 40 quantity it loads anoter 40 from the ship. That 40 is the only quantity available (rest is reserved by other vehicles on their way there). So the other vehicle will only get 40 no matter how large it is. I understand this is a bit unlucky at the same time, this is very hard to fix without lots of complexity and seems like a fairly non-frequent case. So we will not take action at this moment.