First, you should not be calling function_s(conv, "switchDirection") during a simulation run. This is meant for defining the geometric properties of the conveyor, which should not change during the simulation. Instead, you should set the targetSpeed value of the Conveyor object in flexscript. This is intended for dynamic changes during the simulation run.
Second, it looks like there are issues with the entry transfer object not interpreting entry proper entry availability when the conveyor is in reversed mode. To get around that, I added a small single direction conveyor that feeds into the reversible conveyor. This seems to fix the issue.
