Strangers on the Shore - S9-E2
Deliberate mistake: When Del, Rodney and Boycie first arrive in France, there is a side view of the white van they are in and it is clear that the driver is definitely not David Jason.
Deliberate mistake: After Ralph puts the suit into the trash can, when it cuts to Stovington Siding with the hijacked trains one of the shots is flipped, note the "102" is backwards. (00:24:40)