I forgot I had loaded the newest app pro version. The TIUs are still with 6.0. Our grandson was running trains and wanted me to take one of them, while he ran the other.
It worked at first while I used a remote to run the G scale below the O scale with separate TIUs. When I tried to run a train with the remote on the same TIU as the phone was using, things went south. I pressed the read and then he lost control of his train. Meanwhile the remote could not move an engine to active with the remote. It kept saying engine not on track. I cycled the phone app and that came right back.
So I remembered that the new app could run more than one engine. So I selected the inactive engine and it came right up and ran fine with the phone.
The remote could not make that engine active. So is there a problem having the two controllers use the same TIU at once with the pro app??