question

By default, only one item can enter an entry transfer at a time. As such, only one concurrent transport task is created at a time, because the transfer's input is stopped until the pending item has arrived and left the transfer again. (Note how the second task executer only starts to move after the first one has unloaded).

Currently in your model the queue is waiting for the transfer to become available again, which would happen when the second item arrives. The travel won't complete though, because the task executer is blocked by the previous one.

You can either allow multiple transports at the same time by setting the respective option in the entry transfer's properties accordingly.

Or you specifically tell the task executers to return to their starting location when they become idle by using the 'Travel to a Home Location' option in their 'On Resource Available' trigger.