- Failed system: Steering wheel was locked up in the middle of driving. Driver was making a right turn at an intersection. Suddenly a "Steering Assist Reduced" UI_a020 warning appeared on screen, and driver was unable to turn the wheel. No autopilot in any level whatsoever was turned on. - Safety risk: Driver hit another car due to the loss of control of the vehicle. Thankfully it happened in a city intersection. If it happened on a highway, much more damages and casualties might have been incurred. - Reproducing the problem: Right after the accident, driver was ordered to pull the car over to the side. But even after a few restarting of the car, the UI_a020 warning reappeared sporadically. From that time we completely stopped driving the car and drove it only occasionally to load/unload it to tow trucks. So we did not have much chance to reproduce the problem. We have some photos and video clips of the UI_a020 warning taken on the date of the accident. - Has the vehicle or component been inspected by the manufacturer, police, insurance representatives or others?: Not yet. Currently the vehicle is at a Tesla Approved body shop (collision center) for repair. - Any warning lamps, messages or other symptoms of the problem prior to the failure: There was no UI_a020 warning that we recall prior to the time of the accident. This could be unrelated to the UI_a020 issue, but one day before the accident, I was trying to unlock the car using my cell phone, but the car did not recog