One problem related to brake disc pads has been reported for the 1999 Lexus RX300. The most recently reported issues are listed below.
1999 Lexus Rx300. Five days after discs, calipers, pads replaced, the right front caliper fell off while I was driving on interstate 80 at 65 mph. The car began to violently shake and veer to the right. I was able to safely get the car off the road. The Lexus dealer confirmed that the caliper fell off and was wedged between the rim of the wheel and the disc. The bolts were missing. The service manager did not know if the bolts broke from a manufacturing defect or a service defect.