Transmission Stuck In Gear problems of the 2007 Mazda MAZDA3

While driving the car will suddenly jerk as if braking quickly, the check engine light and the at (auto-transmission) light will illuminate on the dashboard. The car will then jump down to 3rd or 4th gear, disallowing it to shift properly. It will remain stuck on the lower gear with the warning lights on until the car is turned off and turned back on. A few times, in conjunction with the aforementioned problem, the car has also lost power steering. This happens on the freeway and has almost caused accidents a few different times. I have taken this to several mechanics and not a single one has been able to diagnose or resolve the issue. The output shaft speed sensor has been replaced, so this is not the issue. There is no predicting when it will happen as it seems to completely random. It has happened on the freeway while going 70 and through neighborhoods when only going 25. It's impossible to predict or give a precursor to what happened immediately prior to the car jumping gears and losing power steering. This is so dangerous.

Nearly every time while driving, a yellow "at" sign will appear as the gear will jump from whatever it is to 3, causing a sudden, sharp jerk (as if one suddenly braked), before going back to whatever gear it was in. This has occured many times one instance at a time, but several times 3-8 times in rapid succession. Also, at times the gear # indicator will flicker and disappear while jumping through different numbers, also causing the traction and at warning lights to appear. During this time, the car will suddenly jerk, slow, and shift unpredictably. The car can also go into "limp mode", in which the gear gets stuck in 3rd for a period of time (usually 2 minutes to until restarting the car). All of these are extremely dangerous for the driver and drivers around them, as the car may suddenly stop or speed up with zero warning to anyone.