https://imgur.com/a/Frsuect

@Fantamos,

I have heard this happening before. It sounds like some sort of pathing issue.

I managed to find a thread on the Paradox forum talking about it:
https://forum.paradoxplaza.com/forum/threads/cities-skylines-steam-postal-vans-trucks-getting-stuck-at-cargo-distribution-centres-internal-cargo-trains.1543398/

Didn't see any solution mentioned though :-(

I turned everything on and off, and even tried to find mods to create workarounds, but nothing appears to exist...

Doesn't seem to be many mods that deal with post vans....

even tried to see if i could switch post vans out for other vehicles, etc...nothing seems to stop post vans from going to depots...which would solve the issue..

I have been having issues with ghost vehicles, that I'm trying to resolve, which causes a nearly similar situation that @Fantamos is describing.

In my case, if you zoom into the building and look inside, and find the first vehicle that is stopped, there will is a "ghost" vehicle box directly in front of the stopped vehicle, that moves back and forth in place which clogs up traffic. For me this happens randomly during the simulation after starting it up, a select industrial building or a cargo terminal (not just post), that looks to be receiving a delivery, but the vehicle doesn't fully release and just bounces in place stopping the next delivery. The vehicle disappears, is not selectable, cannot be deleted due to no tool tip, but the highlight box remains as though there is a vehicle there.

It then causes my traffic percentage to plummet, then I have to go search the map to find where the "ghost" vehicle is and reroute the road via TMPE or Move-it, or rebuild the building in a slightly different spot. Moving the building spawn point only affects the next inbound deliveries, which works on the industry buildings that spawn points are set far back from the road.

Also, the "ghost" vehicle will persists through the maintenance option of resetting broken paths and remove ghost vehicles, and TMPE's reset stuck sims and vehicles. The "ghost" vehicle will remain until the game is restarted.

I have begun to remove all small cargo truck assets to see if I can identify if there is one with a problem similar to the ones identified in the Avayna's US container trucks Packs.

Is there a way to possibly find the ghost vehicle in the output.log? If it would be in there, I can attempt to find it, just need to know what to look for.

@Soulas, doesnt transfer manager have a "release ghost vehicles" button, under the maintenance tab in options.

@Fantamos, Yes, but it wasn't releasing the problematic "ghost" vehicle. Nothing would except for flat out restarting the game. I went on the discord server for this mod and chatted with them, and came to the conclusion that it was a mod/asset conflict, which one, don't know. But the removed mods were, No big trucks, Advanced vehicle options, and transit vehicle spawn delay. I also removed some older cargo truck assets with a pre-2020 creation date, and so far the problem has not occurred.