Task executers do not naturally do anything when they are idle. You must tell them what they should do when they become idle. The control point connections (e.g. ParkPoints) do not have any inherent meaning to the logic of the model unless you define that logic, either by implementing it in a process flow, or using something like the AGV template process flow.
I've implemented a process flow in your model (I did it in 20.0) that listens for the OnResourceAvailable event, then waits for a second to see if he's given anything more to do, and if not, it tells him to go to one of the ParkPoints connected control points. I've made the ParkPoints connection be a list through through the AGV Network Properties window, and I pull from that list to select which ParkPoint to use.

26435-blocking-question-fixed.fsm