The high electrical draw of the CIMs such as when turning or accelerating or pushing can lower the overall system voltage, when it goes lower than a 6.8v the roborios inbuilt brownout protection system starts to cutoff things, until it finally turns off itself, meaning that the robot disconnects from the FMS and the driver station.
It is explained in detail here
http://wpilib.screenstepslive.com/s/...g-current-draw