When I do low power commands the robot wokrs great. The second I take it up a knotch, after the command is executed, it loses power (or connection) and restarts, blinking green and back to cyan. What would this be? A power issue or connectivity? The power source is regulated at 5V from a sabertooth 25x2 board.
It sounds to me like you have a power problem. You don’t say how big the power supply is in amps or what motors you are driving on the robot, but motors often require very large start-up current called the LRA for locked rotor amperage.
Can you try temporarily powering the core from a completely separate power source to test this? Just make sure the grounds are tied together.