You haven't read my posts then. I had 3 units at one time and none of them ran together. After cleaning up the paste performance improved but I still had problems. I've since sold 1 unit, but since replacing the USB cable I successfully run 2 U3's and 1 Rockminer R-Box together. Every 4 days or so I do have to cycle power on the U3's and unplug/replug the USBs, but that is acceptable to me.
Just edited my post as I read through this thread again, searching for answers. If I understand you, you had 3 and they wouldn't run together, you cleaned up thermal paste, and then they ran together? You say "performance improved", but what does that mean exactly? If the only change you made to get them to run together was cleaning thermal paste I'll give it a shot.
What happens every 4 days that you need to cycle them? Performance drops? Errors? Zombie?
Performance undeniably improved after cleaning the thermal paste. By this I mean the units lasted longer but still Zombie'd. Replacing the USB cables then let me get to where I am at today. It might be worth just changing the USB cables without doing the paste to see if that would have been enough as cleaning the paste is a pain and is not for everyone.
I never got 3 to run together because I sold one before I got the new USB cables.
Now after running for a few days one of the units will Zombie. Unplugging/replugging gets it to work again but only for a short while. Cycling power and USB plug/replug gets it to work for another 4 days or so.
Hope this helps.