LEGO MCL39 - 42228

Hi, I first of all want to say that I don’t think this is a differential question, which I know gets posted a lot when this problem arises…but I’m willing to be told otherwise if I’m wrong! 😂 From the video, hopefully you can see that the differential is working but the cogs that turn the engine are not turning when the wheels are. But, the engine does work when the coloured cogs are moved. The grey barrel in between the green and red cog moves with the wheels but nothing seems to be...