I had initially no COM port at all. By a closer inspection it was assigned to COM7 which also was used for 4 virtual cables on that specific Laptop (SDR Console an other SDR stuff) from COM6 to COM8. Manually changed the port to COM9 and it was duplicated as you know and everything running fine. Before I often got the COM port twice but only after a crash.
I found there is some problem with aborting a scan. This often leads to all kind of problems. Best way to abort a scan is to tap the screen of the tinySA. The RBW setting on tinySA.exe is also not working. More work to do