[Al Skierkiewicz]

Michael,
If the battery voltage should fall to 5.5 volts or less, the connection on the Crio analog module #1 will sense this and disable all outputs. In your particular case, are you sure that all motors are connected in the same direction? It sounds like one of the motors is running in the wrong direction such that when placed on the floor, you are generating enough load to cause the battery voltage to fall. When the robot is off the floor, I bet one side is running much slower than the other side. It is also possible that you have a loose electrical connection somewhere in the battery path. (bad Anderson connector, loose battery terminal, loose hardware on the PD, loose hardware on the main breaker) A loose connection will drop significant voltage when you are drawing a lot of current. This symptom also occurs with a discharged battery so it confuses a lot of teams as to exactly which part of the electrical system in which the failure is occurring. I am assuming you are using the 24 volt output on the PD for the Crio as well.
There is always the possibility under these conditions, that part of the drive is binding with the weight of the robot on the floor.