Crisp, ANS: Being a "mistake" is a RELATIVE view. Please Register or Log in to view the hidden image! pun intended.
There are no mistakes anywhere, I am not assuming u 'have' to see the event simultaneously from two frames of reference! Ok how about looking at it from this perspective. If a car is fully inside the garage at any time then it gets blown up. What happens?
OK lets say at each end of the garage there are terminals with a high potential difference across them. At each end of the car there are highly conductive rods (rather like a lightning conductors) which are connected by a wire. Along this wire (in the center of the car) is an explosive device which only detonates when current flows though it. Only when the rods touch the garage terminals does the car blow up. In one frame the car never touches the terminals and never blows up. In another it blows up. Which is reality and which is not or do we invoke the many worlds theory here again?!!!
In both frames either the car blows up or it doesn't. Remember, electricity is bound by the same laws of physics and can't travel instantaeously either. Thus it takes time for current to develop. For instance, When one end of the car touches the positive terminal, it causes a disturbance in the electrons at that end of the car, and this disturbance will travel through the car towards the other end at some velocity below c. The same happens at the negative end. When these disturbances meet at the center, we can say that a current is flowing at the center. (And the bomb blows up. ) From the frame of the car, this happens because the two terminals are touched at the same time and it takes an equal time for each pulse to reach the device. From the frame of the garage the two terminals do not touch at the same time, but in sequence. But neither will the disturbances be seen to travel at the same speed with respect to the car (addition of velocities theorum). The result is the from the frame of the garage, the disturbances still meet at the center of the car at the same time, and the car blows up. If you want to add the requirement that the current must exist across the whole length fo the car in order for the device to detonate, then the ends of the car must slide over the terminals for some given time, long enough for the current to develp. From the frame of the car the length of the terminal would then say, have to be x. But these terminals are moving with respect to the car, and undergo length contraction, thus they must be somewhat longer than x in the garage frame. What this means is that from the garage frame, that while the two ends of the car will first contact the terminals at different times, before the first one breaks contact, the second one will make contact, and there will be a time while both are in contact. Again, you will still see conditions that will lead to the detonation of the explosive device from both frames.
