Issue with RHW OWR FLUPs Portal (Draggable/Subway version)

[Mouse-Diplodicus]

Description

For some reason, the "One-Way Road (OWR) Flexible underpass (FLUPs) Portal (FLEX-based)" piece (for the subway-based FLUPs) does not appear to work properly. The "Flexible Underpass" and "Road Flexible Underpass" pieces work with both the "URoad-2" and "URoad-4" Starters/Subway networks, but when I try to use the one-way underpass I cannot get traffic to flow along the network.

Steps to reproduce

Unless I misunderstood the directions the steps I took should be the same as those given in the documentation, in summary:

1. Place two OWR FLUPs Portals across from each other (Are there different pieces for the entrance and exit?).
2. Place the "URoad-4" starter piece in between the portals (I don't know if the rotation of this piece matters but I have tried both orientations and neither works)
3. Drag the Subway Network between the two portals and through the starter piece to finish the network.

Expected result

Traffic should be using the one-way underpass.

Actual result

Traffic is not using the one-way underpass.