Originally Posted by Mr V
Hot wires are also a symptom of high resistance. Since you say some of the wires are not getting hot then excessive current draw is not the problem as all of the wires would be heating up similar amounts since they are all the same gauge.
The proper way to find the problem is voltage drop testing. Put the robot up on blocks. Put your volt meter + probe on the battery + terminal and the - probe on the main breaker battery terminal. Then run the robot at full speed for a few seconds and observe the voltage on the meter. Repeat with the + probe on the PDP - terminal and the - probe on the battery - terminal and observe the voltage.
Regarding this - one of the more common places we've found high resistance is corrosion on the Keps nuts on the main breaker leads. If you leave it for long enough the plastic of the breaker will melt (that's how we found the issue).