XD1035 USB serial issue

After connecting an USB serail converter with FTDI chipset I am not able to get any data out of the serial port.

Logfile:

[10808.741] usb 4-1: new full-speed USB device number 5 using ohci-platform

[10808.984] ftdi_sio 4-1:1.0: FTDI USB Serial Device converter detected

[10808.984] usb 4-1: Detected FT232RL

[10808.985] Target /devices/platform/fe3e0000.usb/usb4/4-1 ID 0

[10808.985] DisplayImpl::ChangeDevice but unrecognised path /sys/devices/platform/fe3e0000.usb/usb4/4-1

[10808.985] Target /devices/platform/fe3e0000.usb/usb4/4-1 ID 0

[10808.990] usb 4-1: FTDI USB Serial Device converter now attached to ttyUSB0

[10808.996] USB vidpid=0403:6001

[10809.005] handle_tty /devices/platform/fe3e0000.usb/usb4/4-1/4-1:1.0/ttyUSB0/tty/ttyUSB0

[10809.014] Target /devices/platform/fe3e0000.usb/usb4/4-1 ID 0

[10809.026] HOTPLUG TTY: 0403:6001:1.0

[10809.041] No action from registry for hotplug_tty:0403:6001:1.0

[10809.409] Failed to set serial port mode: tcgetattr: Bad file descriptor (9)

[10810.038] Autorun.payload-cellular : INFO Did not find any active supported modems

[10814.314] BrightScript creation of roSerialPort failed:

[10814.314] Failed to open serial port

[10816.847] BrightScript creation of roSerialPort failed:

[10816.847] Failed to open serial port

Why does it always says "BrightScript creation of roSerialPort failed: Failed to open serial port"?

Software: BrightAuthor Connected 1.27.1

Player: XD1035

Boot Version: 9.0.85
BrightSignOS Version: 9.0.120

Thanks

Timo