It's a connector issue so far every time. Stern has had this issue since they moved to SPI controlled LED boards back in Spike 1. This machine however has a completely brain free design, where they use the lowest node board's SPI and daisy chain it over 5 or 6 LED boards, until it finally lands to the controller board that moves Groot's mouth.
Normally a small hickup in the bus is not a problem, it just causes a very brief incorrect flicker of some LEDs. When it's real bad, couple of LED boards go nuts but it still doesn't do much to the game.
But since the motor control board is at the very end, it starts getting spurious commands and starts moving on its own like in the video, literally making the game unplayable. The issue was discovered in freshly unboxed games as this is a design issue and not a fault per se, but as the game ages, there will be connector wear and more cases of a bit going sideways somewhere.
The power isn't daisychained, the motor has its own PSU but that won't help much when the controller receives garbage control commands at random.