so my team is awake at 1 right now and our competition is today. our robot was working perfectly for 2 weeks until yesterdaty when we went through inspection. The dude did this ptc test and stopped all the motors till their limit. After that, everything fell apart. The left side of Our 4 bar doesn’t work when the rd4b is less than 2 feet off the ground but works everywhere else. The rd4b also randomly stops working at the lowest position. Both sides of our drive also randomly independently die after like 30 seconds of driving and our robot cannot go straight at full speed. We have updated firmware on both the cortex and the joystick and replaced motor controllers and motors but the problem persists. what can we do? we were considering repkacing the cortex. do you think this might solve the problem?
you might have tripped the ptc on the cortex. This will take some time to reform. also try to cool off your motors with some compressed air cleaner.
the problem about the things dying when the lift is above 2 feet may have to do with wiring, maybe a wire disconnects after that height
we have checked that…nothing is disconnecting
Make sure that you are not overloading the cortex PTC on each of its sides. 1-5 motor ports have a PTC and 6-10 have the other PTC. If you’re using a Power Expander make sure you don’t have all the base motors on the Power Expander or on ports 1-5 or 6-10 divide them evenly so the PTC’s don’t trip. The PTC test should not affect the motors and should only take about 15-20 minutes to recover as stated in the PTC Verification Guide
I assume the PTC test caused some form of mechanical failure. Check the internal gears of your motors to see if they got rekt when they tested your PTCs.
I’m sorry if I’m too late; I just saw this thread. This happened to another team in my region a few years ago. They tried replacing the motor controllers, and then ultimately the cortex. Sometimes, the entire cortex internals can be fried due to PTC testing.
This statement is false - if you read the VEX PTC test procedure, you will see that motor is disconnected from the Cortex to test the motor’s PTC. As mentioned earlier, the PTC in the motor will recover virtually completely within 15-20 minutes.
When PTC checking, the motor is stalled on purpose by restricting the motor from spinning up. Internal gearing should not be impacted.
Note that the above assumes a correct PTC procedure. I am concerned by the statement from the original poster:
which sounds like the motor being tested was not isolated from the rest.
Welp, I don’t know what I was thinking. Thanks for the correction. 
This has happened to me so many times… whenever it happens to me I just have to replace the motors, and sometimes motor controllers. For some reason whenever I put load on those motors that are doing the weird things like that, they just stop… try replacing motor controllers… then motors… then cortex (IF YOU ARE SURE CODE ISN’T THE ISSUE, AND A MULTIMETER IS SAYING THERE IS CURRENT)