On normal brake applications when stopping the brakes grab and make a knocking/thumping noise and when i get up off the brakes it stops only on the right rear disc brake.
brakes grabbing on 1994 Lexus LS400
sounds like you have hyraulic issues. take it to a shop and have them check the master cylinder for operation and the brake hoses and calipers.
Sounds like caliper movement problems causing uneven braking and/or hanging up even when pedal is released. As mastertech6371 says-get it checked asap.