I haven't noticed the three and go. But I have noticed something like that with the configuration manager. Seems likely Bob is correct that such a problem most likely derived from the serial connection.
As for the green light coming on then going out....try using the poth simulator instead of the mount. See if it tanks too. If it does then....it isn't the PMC8 driver. If it doesn't....?
Wes, Southport NC
PMC-8, ES ED 127, 10" LX200GPS, Astro-Tech 8" Newt, ETX-90
Polemaster, Orion ST-80 and SAG
Electrical Engineer, Retired