In the attached model only patients with PCI 3 are being processed. When patient ID 35 completes the 2nd floor process. The patient and the companion go to the elevator. The companion enters the elevator and the patient waits for the next elevator. When the companion gets to the 3rd floor process (before the patient), the program stops and a dialogue box pops up saying the destination for that companion could not be determined . This same event happens for patient 217 and patient 323. If I remove the Repeat Random Streams, the event occurs with different patients during the day. Thanks for your help with this. This problem has cost me considerable hours but I didn't want to send it in until I had what I think is a good example to show what is happening. Teeelevators-th-02-21-2017.fsm