PSDK V3.5 / M300 RTK / FTDI FT4232H - UART issues

Hello,

I'm using an FTDI FT4232H to connect to the UART port of the DJI M300 RTK. The USB part of the connection is fine. In Ubuntu I see the USB Ethernet with an interface name enxd2e780cae600 (it is the ttyACM1 in my case). 
The FTDI FT4232H is shown in Ubuntu with /dev/ttyUSB0 to ttyUSB3. The port is manually configured by "sudo stty -F /dev/ttyUSB0 921600". If I controll the setting with "sudo stty -F /dev/ttyUSB0" I get the 921600 back. I can connect with "picocom -b 921600 /dev/ttyUSB0" and see that there is binary data received.
hal_network.h, hal_uart.h, hal_usb_bulk.h, dji_sdk_app_info.h and dji_sdk_config.h are configured with the settings. When the sample code is started with "sudo ./dji_sdk_demo_linux_cxx" the following information is printed on the screen:

sudo ./dji_sdk_demo_linux_cxx
[0.003][core]-[Info]-[DjiCore_Init:101) Payload SDK Version : V3.5.0-beta.0-build.1764
[1.685][adapter]-[Info]-[DjiAccessAdapter_Init:170) Try identify UART0 connection failed. Probably because SDK adapter or aircraft not finish init or UART connect error.
[3.417][adapter]-[Info]-[DjiAccessAdapter_Init:170) Try identify UART0 connection failed. Probably because SDK adapter or aircraft not finish init or UART connect error.
[5.151][adapter]-[Info]-[DjiAccessAdapter_Init:170) Try identify UART0 connection failed. Probably because SDK adapter or aircraft not finish init or UART connect error.
[6.376][linker]-[Error]-[DjiProtocol_sdkUnpack:228) protocol frame crc16 error:0x434F 0x8246
[6.885][adapter]-[Info]-[DjiAccessAdapter_Init:170) Try identify UART0 connection failed. Probably because SDK adapter or aircraft not finish init or UART connect error.
[8.616][adapter]-[Info]-[DjiAccessAdapter_Init:170) Try identify UART0 connection failed. Probably because SDK adapter or aircraft not finish init or UART connect error.
[10.352][adapter]-[Info]-[DjiAccessAdapter_Init:170) Try identify UART0 connection failed. Probably because SDK adapter or aircraft not finish init or UART connect error.
[11.595][linker]-[Error]-[DjiProtocol_sdkUnpack:228) protocol frame crc16 error:0xD2AA 0x5B29
[12.088][adapter]-[Info]-[DjiAccessAdapter_Init:170) Try identify UART0 connection failed. Probably because SDK adapter or aircraft not finish init or UART connect error.
[13.821][adapter]-[Info]-[DjiAccessAdapter_Init:170) Try identify UART0 connection failed. Probably because SDK adapter or aircraft not finish init or UART connect error.
[15.550][adapter]-[Info]-[DjiAccessAdapter_Init:170) Try identify UART0 connection failed. Probably because SDK adapter or aircraft not finish init or UART connect error.
[15.550][adapter]-[Error]-[DjiAccessAdapter_Init:175) Try identify UART0 connection timeout. Probably because SDK adapter or aircraft not finish init or UART connect error.
[15.550][core]-[Error]-[DjiCore_Init:121) Access adapter init error, stat:225
terminate called after throwing an instance of 'std::runtime_error'
  what():  Core init error.

If I start "sudo stty -F /dev/ttyUSB0" again the baud rate is now set to 1000000.

What happens in the psdk_lib that the baudrate is changing? If I'm using a CP2102 USB to serial converter the sample code is running without any issue. What must be done that the FTDI FT4232H is working with the sample code?

BR, Michael

PS:
Output of lsusb:
 lsusb
Bus 002 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
Bus 001 Device 007: ID 8087:0026 Intel Corp. AX201 Bluetooth
Bus 001 Device 010: ID 2ca3:001f DJI Technology Co., Ltd. e1e
Bus 001 Device 009: ID 0403:6011 Future Technology Devices International, Ltd FT4232H Quad HS USB-UART/FIFO IC
Bus 001 Device 008: ID 0424:2507 Microchip Technology, Inc. (formerly SMSC) hub
Bus 001 Device 006: ID 1a40:0101 Terminus Technology Inc. Hub
Bus 001 Device 005: ID 3343:803a Unknown LattePanda Leonardo
Bus 001 Device 004: ID 0bda:0129 Realtek Semiconductor Corp. RTS5129 Card Reader Controller
Bus 001 Device 003: ID 046a:00b6 Cherry GmbH USB Mouse
Bus 001 Device 002: ID 046a:0023 Cherry GmbH Keyboard
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub

/dev/input/event3 - CHERRY_USB_Mouse
/dev/input/event4 - 046a_0023
/dev/input/event5 - 046a_0023
/dev/input/mouse0 - CHERRY_USB_Mouse
/dev/sda - Linux_File-Stor_Gadget_123456789ABCDEF-0:0
/dev/sdb - Linux_File-Stor_Gadget_123456789ABCDEF-0:1
/dev/ttyACM0 - Unknown_LattePanda_Leonardo
/dev/ttyACM1 - DJI_e1e_123456789ABCDEF
/dev/ttyUSB0 - FTDI_Quad_RS232-HS
/dev/ttyUSB1 - FTDI_Quad_RS232-HS
/dev/ttyUSB2 - FTDI_Quad_RS232-HS
/dev/ttyUSB3 - FTDI_Quad_RS232-HS