That’s what the error (“Cannot lock port”) indeed suggests.
I don’t know if HAOS comes with common Linux tools, but if so, open a Terminal and run the following: sudo lsof /dev/ttyUSB0
The command lsof (“list open files”) should show if there are any processes that are using the device.
Could it be that ZHA is enabled? Look here for more information, it sounds very similar to your situation.