Julius recreates many bugs that you can find in original Caesar 3 game, to preserve 100% saves compatibility. This is an incomplete list of those bugs and some gameplay idiosyncrasies that you can encounter during the gameplay. Feel free to send a pull request with other bug reports that update this list.
Each building in Caesar 3 is assigned to only one road network. That can result in a situation where a warehouseman cannot reach a given warehouse just because the warehouse has been assigned to another network than the building that's sending a warehouseman (see the image below). To avoid this problem make sure that all your warehouses are adjacent to only one road network.
Gardens split roads into separate road networks. Even though marker trader can use garden tiles as road tiles and pass by a given warehouse, that warehouse (even if full) might be ignored if it's assigned to another road network than market building (each building is assigned to a single road network in Caesar 3). To avoid this problem make sure that market traders traverse your city via road tiles rather than gardens.
In original Caesar 3 game, market trader can get food only from granaries, never from warehouses (even though market traders get resources from a warehouse, such as pottery).