The conveyor should be reversed after the item has left it. For example in a trigger of the processor. You can copy the pickoption code from the photo eye. You just need change how the conveyor is referenced. A centerport connections between processor and conveyor would make sense.
After the item enters the conveyor again it needs to be send to Conveyor2. You can use the "Send Item" trigger option on a photo eye or decision point for this. This should only happen on the return trip. So you could use a negative conveyor speed as condition for the trigger. A trigger on the photo eye/decision point on Conveyor2 that the item is send to can reverse Conveyor1 again. Again, a centerport connection seems suitable to refer to the correct conveyor.
Finally, you would need to make sure that no other items enter the reversible conveyor before the previous item has been processed and exited the intersection. If you want to leave Conveyor1 as one object I would suggest to close the output of the source in its exit trigger and open it again at the same time that the original speed of Conveyor1 is restored.
Or you split Conveyor1 into to conveyors, with the first only leading up to the intersection. Then use the area restriction trigger options on photo eyes or decision points to stop further items until the previous one has entered Conveyor2.
