Deliberate mistake: When the appliance crashes into the drunk driver's car and flips over, water is seen spilling out of the top of the appliance. This appliance was specially designed to flip over by mounting the water tank at the top, to make it unstable enough to tip over.
Episode #4.3 - S4-E3
Deliberate mistake: Before the gas explodes in the sewer, you can see the base of the Davy lamp glow red. Except that in real life this doesn't happen; the flame simply turns blue and grows taller in the presence of gas. This was probably done to make the scene more dramatic, though.
Episode #8.7 - S8-E7
Deliberate mistake: The washing machine must have been primed with explosives and petrol in order to catch fire. The machine is not actually on. Also, there are no electrical connections behind the drain filter cover (where the machine starts smoking and sparking). There is just a removable plastic filter and nothing else. (All washing machines have this). (00:35:15)