Flashed v7.1 to no avail. The Taranix establishes a connection, shows some values but after ~5secs: Connection lost.
In some rare moments it keeps the connection but doesn´t display any status changes - it stays at "Disarmed", sometimes goes to "Unknown" for unknown reasons.
The hex file from Johannes should work like it does for Larry. The only difference I can see: he´s using the standard version, mine is the Plus version. But that shouldn´t be the problem here, right?
Sorry to waste your time, Max.

At least it works for 2 persons now. Good job!
Will follow Johannes´hint and try to erase the Teensy first bf I flash his hex file again...