This is a common issue when doing the burglar missions.
Sometimes when leaving houses when youre robbing a house, your truck will fall through the map and often not come back before a complete server restart.
I’m thinking this has something to do with it becoming out of render distance when you enter a house, because you get teleported away.
can confirm this occurs still as of last night, and have seen the truck falling through the map when exiting the building.
can get video if needed, though you said this is an older/known issue
tested with a world spawned gopostal boxville last night and it despawned upon walking outside.
i did wake up the resident though, so i will try and test again tonight if that plays part, but ive failed in the past and it remained where it was parked.
Have not tested with a self-purchased boxville either