Three were bad, one worked fine. Have changed three bad, now all works. But before flight I read that there are different versions of the ESCs. On the new ESC-package it says 2.0, on the ESCs in these packages it says 2.1 and the one left (the one working) on the Phantom, there is no version-number on this area. Quaestion: Should I change No 4 too? Is there a difference in behavior?