Trucks not emptying completely before returning to excavator

Issue description

Trucks assigned to a tower with multiple storages don't empty all their content in the designated storages before returning.
So a truck with say coal and dirt will empty the biggest portion (say 13 coal) into the coal storage, but the 7 dirt will be trucked back to the excavator instead of being dumped in the dirt storage (which is right beside the coal one).
Seems to be that the biggest load gets unloaded, the small load(s) not.
This is wasteful behavior since it limits the truckcapacity meaning a whole lot more movement.
I have partial truckloads not allowed if that is relevant.

Reproduction steps

1. load save from zipfile
2. go to coal
3. see behavior described above.

Game version and build number

v0.6.0b b317

Operating system

Windows

Attachments

save_23-05-25_20-26-25.save

I've observed this behavior as well.

I'm seeing this happen quite frequently, including as of the recent patch (b322). It's not game-breaking but does impair mining efficiency.

Is the dirt storage not full?

I'm seeing the same on Windows Version 0.6.1 (b323), with partial loads allowed. Unlike the original report, on mine it is not necessarily the largest part of the load that is only delivered.

Save game here (see the iron ore mine, hopefully at the view location where I saved): not unloading.save

From that save point, the 11th(ish) pickup that goes to do a dropoff does behave as expected, but then following ones are partial. Maybe one in ten mixed loads are delivered as expected.

The destination loose storage for dirt/rock/iron ore all all beside each other, empty (or nearly empty), and very close to and on a level path to the mining site. Tower has 5 diggers and 10 pickups assigned, and all the diggers are working.

The behaviour also persists when:

• The destinations "accept assigned only" is on or off
• The destinations are explicitly set as export target for the mine tower
• Control tower has no export targets sets (the trucks still use the same loose storages, but only partially unload)

In case it matters, I normally have these loose storage set as tower export targets, and the three misbehaving ones were copy+pasted from elsewhere on the map taking the tower export-to designation with them. I'd only recently removed the export-to before doing this save. All three loose storages were also iron-ore (due to the copy+paste), but then I changed the two on the right to be rock/dirt.

Edit to add: Alternate drop-off locations that are empty and have a clear path to them are also being ignored, in case a bug makes it think those three are full. The copper ore mine in the far far "north" is doing it as well.