Geräte unter Linux werden mit einer udev rule im Verzeichnis /dev/serial/by-id einsortiert. Dabei wird das Gerät nach der Serial-ID nahezu einduetig im Baum dargestellt. Danach ist es egal welche USB-Port man nutzt.
Die Datei /lib/udev/rules.d/60-serial.rules korrigieren.
sudo nano /lib/udev/rules.d/60-serial.rules
# do not edit this file, it will be overwritten on update
ACTION=="remove", GOTO="serial_end"
SUBSYSTEM!="tty", GOTO="serial_end"
SUBSYSTEMS=="pci", ENV{ID_BUS}="pci", ENV{ID_VENDOR_ID}="$attr{vendor}", ENV{ID_MODEL_ID}="$attr{device}"
# We already ran the hwdb builtin for devices with MODALIAS in 50-default.rules.
# Let's cover the remaining case here, where we walk up the tree to find a node with $MODALIAS.
ENV{MODALIAS}=="", SUBSYSTEMS=="pci", IMPORT{builtin}="hwdb --subsystem=pci"
# /dev/serial/by-path/, /dev/serial/by-id/ for USB devices
KERNEL!="ttyUSB[0-9]*|ttyACM[0-9]*", GOTO="serial_end"
SUBSYSTEMS=="usb-serial", ENV{.ID_PORT}="$attr{port_number}"
IMPORT{builtin}="path_id"
ENV{ID_PATH}=="?*", ENV{.ID_PORT}=="", SYMLINK+="serial/by-path/$env{ID_PATH}"
ENV{ID_PATH}=="?*", ENV{.ID_PORT}=="?*", SYMLINK+="serial/by-path/$env{ID_PATH}-port$env{.ID_PORT}"
IMPORT{builtin}="usb_id"
SUBSYSTEMS=="usb", ENV{ID_BUS}="usb"
ENV{ID_USB_INTERFACE_NUM}=="", GOTO="serial_end"
ENV{.ID_PORT}=="", SYMLINK+="serial/by-id/$env{ID_BUS}-$env{ID_USB_SERIAL}-if$env{ID_USB_INTERFACE_NUM}"
ENV{.ID_PORT}=="?*", SYMLINK+="serial/by-id/$env{ID_BUS}-$env{ID_USB_SERIAL}-if$env{ID_USB_INTERFACE_NUM}-port$env{.ID_PORT}"
LABEL="serial_end"
After that do
sudo udevadm control --reload-rules && sudo udevadm trigger
Then it worked for me.