I had an Acura RSX-S before the Subaru. This issue happened to me. The little bracket on the back of the pedal was loose causing it to kind of tilt towards the floor matt. I had all season matts with the deep ridges and the pedal would sometimes get stuck a little bit in one of the ridges. Not saying thats your issue but you should check it out and see when the car is off if you can push the pedal to the floor a few times and get it to stick. If so then you can either tighten the bracket on the back of the pedal if the Subaru's have them or simply take the matt out..