Hello, I have 2013 lexus GS 450h, I am totally happy with this vehicle, but it has strange short click noise when I press the accelerator or brake pedal. when I heavily braking it may has 2 or 3 clicks, but on accelerating it just clicks once. the sound is in both, electric and gas mode. I suggest that it would be the driveshaft U joint, have your car ever been in this kind of situation? I can't hear where it comes from and the vehicle doesn't has any kind of resistance, it just clicks.
Here is a video - https://photos.app.goo.gl/z87chLpVZ14SCapd8
Sorry for my broken English.