When the teenager's car is first seen, it is further away from the part that has only 1 cross bar. When the car hits the fence, the teenager's car is now several feet closer.
The police car Hunter is shown driving is a 1977 Dodge Monaco, which would have been 12 years old as of the air date. While a running gag early in the series was Hunter driving clunkers, by Season 5 the tone had changed to a more serious nature. The LAPD would not utilize a 12 year old car for a homicide detective. At most such a car would be 5 years old.
The fence where the car goes over the cliff has a section where there is only 1 crossbar instead of two. The car hits this section, but before it does so, it begins to get airborne via a ramp. A car crashing into a fence on level ground would not get airborne.
The car is idling in gear and then heard to accelerate before it goes over the cliff. If the driver had been incapacitated prior to this and the accelerator pedal jammed open, the acceleration sound could not have been possible. The sound was that of someone depressing the accelerator rapidly, which would not be possible unless the driver was doing so.
A significant point of the investigation was the amount of time from the restaurant to the crash scene. The valet said it was 9:11 and the radio broadcast in the teenager's car said it was 9:26 for an elapsed time of about 15 minutes. Hunter timed the drive using a stopwatch and got about 7 minutes and 29 seconds. However, several things could have affected this time. The driver may have taken a few minutes before departing the parking lot. Also, watches and clocks usually vary by several minutes, especially in 1989 before things such as Atomic clocks were prevalent. The only way to remove any discrepancy would be to compare the valet's watch to the time broadcast by the radio station.
Search warrants cannot be ordered over the radio as was shown after Rick spoke to Lockwood. The detective would have to prepare the warrant and have a judge sign it, as the warrant is based upon the personal knowledge of the detective.
Rick's diagram of the crash does not line up with what was shown. He shows the teenager's car parallel to the cliff when in fact it was facing the cliff.