So, a few thoughts based on experience:
- The first part of the video seemed like an electrical issue, like a dead battery or a short. The behavior was not indicative of a mechanical failure, at least none I've seen.
- The sounds in the second part sounds like one of three things, it could be either one of the motors not being powered (assuming you use 2 per gearbox), a CIM that has lost it's key between the shaft and the pinion gear (and is free-spinning), or gears not engaging each other in the gearbox for some reason (probably due to lost teeth or loose motors).
I would be curious if the issue persists if the robot is up on blocks (wheels not touching anything), I would also be curious if you could identify a certain action that causes the issue to happen consistently (turning the robot, for example) or if it just happens at random. I would also suggest monitoring battery voltage during such tests through the driver station.
On a somewhat related note, our team experienced some odd behavior (seemingly random jerkiness during acceleration) with our drive system this year when using Talon SRX controllers in CAN configuration. We later realized the issue only occurred when the controllers were fed a 100% power command. We changed the code to limit the max output to 99.9999% power and the issue vanished.
