During Smoke Testing of 3.6.4 we are getting a Baud Connection fail error at the first attempt to connect to the printer. I attempted to flash FW to see if that would help but got a communications error. I then pulled the USB cable out of the computer and connected it to a different USB port and was able to connect to the printer successfully. This happened in our Ubuntu 16.04 system, Mac OS X High Sierra & El Capitan systems so far.
Here is the log for Ubuntu 16.4/Mini with aerostruder v1 toolhead
Here is the log for Mac OS X High Sierra/Mini2 with 0.25 toolhead
Here is the log for Mac OS X El Cap/Mini with standard mini extruder
A few more observations, this DID NOT occur in Windows 10/Mini with standard Mini toolhead.
Also, we tried pulling the USB cable and reconnecting to the same port and the connection failed. It only reconnected if USB was plugged into a different port.