I just managed to solve my problem. 
So I want to share my solution:
After a bit of research yesterday I found out, that since the last MacOS Update to Sierra Apple added their own FTDI driver to the System.
So the solution was, to remove the other two FTDI-Drivers I had installed from the kernel extensions.
And now it connects / disconnects without a single problem and without a restart 
I am pretty happy
Here are the links that lead me to the solution:
https://superuser.com/questions/1135730/how-to-release-reset-serial-port-ftdi-devices-mac-osx