When the dispatcher sends a train to stop, and the destination causes some wagons to uncouple via the Automatic Coupling System mod, the uncoupled wagons are stored in the Dispatcher memory as "being dispatched" even though they are at their destination and have no locomotive. Dispatcher code sets them to automatic, which means they produce a continuous "no path" error message (because without a locomotive they can't go either way), and more importantly, inserters cannot interact with them. Also, when you manually recouple to the wagons, Dispatcher resets the schedule to match the train that last uncouple those wagons.
This is a bug I submitted on GitHub in April, and yesterday I submitted a pull request with a tested fix for it. I added tests so that trains that have no locomotives are omitted/removed from the dispatching queues and set to manual mode.
