Within the past two weeks I noticed that when my Model S starts up there is often a knocking sound in the front, coming from somewhere under the dash and right behind the steering wheel. It also happens at certain times while I am driving at slower speeds and when braking, so it could be something in the braking system. Has anyone else had this happen? This is even with the new firmware version 7.1. When I started the update and as the systems were restarting the first time, I noticed the knocking sound then too. The good news is that aside from this unusual sound, everything else seems to be working well. There have been no messages or alerts either.