Raspi4 conbee 2 failed to reconnect to network

I’m new to deconz and conbee 2 and try to get it up on my raspberry 4 with dietpi. After reading the advice from here:
and here:

I think I have done everything that I can do. dietpi ist uptodate, deconz fresh installed, firmware of conbee 2 flashed today.

I start deconz after reading above forum thread like this:

 deCONZ --dev=/dev/ttyACM0

I still get in deconz debug view level INFO this:

09:44:54:673 wait reconnect 1 seconds
09:44:54:796 COM: /dev/ttyACM0 : ConBee II : dresden elektronik ingenieurtechnik GmbH (0x1CF1/0x0030)
09:44:54:814 COM: /dev/serial/by-id/usb-dresden_elektronik_ingenieurtechnik_GmbH_ConBee_II_DE2668136-if00 / serialno: DE2668136, ConBee II
09:44:54:818 auto connect com /dev/ttyACM0
09:44:55:674 failed to reconnect to network try=6
09:45:00:674 try to reconnect to network try=7```

Strange things. After trying all usb ports of the raspi, trying some different cables and finally flashing firmware for a second time deconz now connects to the conbee 2.

Can check the firmware using GCFFlasher_internal -l or trying the conbee on another host.

Else for the USB port/cable all is possible, USB2/USB3, issue on cable, I know an user that have better result depending the conbee orientation.