Hi Tableworm - welcome to the forum!
Just checking that if you connect the original green car to the other controllers (red, blue or yellow) that it changes lanes successfully?And that the other three cars when connected to red, blue or yellow change lanes okay, but fail to change lanes when connected to green. This happens when using the app AND when running outside the app (ie with the powerbase switched on, but without the ARC app launched on your smart device).
Also, when you connect one of the other controllers (red, blue or yellow) to green on the powerbase, lane changing does not work? When connecting another controller to the powerbase, make sure the original green controller is switched off.
If the problem occurs when you run without the app and with all the controllers and cars, I suspect a powerbase fault - you’d need to contact Customer Services (details right or below). However, if the problem occurs only in the app or only with certain cars or controllers, we have more problem-solving to do... a replacement powerbase will have exactly the same problems.
I hope that helps!