I have asked him about external units...It's a very strange story. I don't think the display/motor can understand that a non-original App is connected to it. Put a flag in memory after such connection, also a strange practice, because the Bluetooth protocol often have errors in the data transfer. I have checked all the commands that Etube sends into STEPS system and didn't find any unknown/suspicious.
The bike may have been equipped with external units to cheat the speed (Speedbox and etc). This can be recognized by the firmware and in this case the corresponding error will appear, which was read during diagnostics.
If he will answer I will public his answer here...