I found this episode which has a deep muddy scene, if not exactly quicksand? A police on a motorbike giving chase falls in a pond and becomes trapped in deep mud. It starts about 35 mins in and seems to go on and off through the rest of the episode to when he's rescued by the fire brigade using their long ladders. https://www.youtube.com/watch?v=CCppIew2W3M
BTW, the fire brigade couldn't use a ladder because it would have sunk into the mud. Instead, they used a pair of fire hoses with the ends plugged, that were inflated with air from a compressed air tank.