When Jack has an accident skiing and falls down, snow is covering his sweater and pants. A few minutes later when he is being lifted into the doctor's office, there is no snow or any moisture anywhere on his clothing.
At the very beginning of "Autumn," we see leaves falling as a blue Mercedes sedan whooshes by (the camera catches the right side of the car) on a curvy road. All we see is the right side/front of what is very clearly a late '70s/early '80s S-class Mercedes (likely a 450 SEL or a turbodiesel variant of the same body style). However, in the next shot, the car shown is the same color, but very clearly a 300 class (300 Diesel or 300 Turbodiesel) model. The latter is used in all interior and exterior shots throughout the Autumn (at the Connecticut inn) and eventually sinks on thin ice in "Winter."