I have an almost new Trek Liquid 10 with the Fox Talus rear shock. On every compression stroke of the rear end, there is a "marble in a coffee can" sound, apparently coming from the rear shock. It occurs just as the shock is starting to compress on any hit except an extremely slow hit. I can make it happen by either lifting the rear tire off the ground an inch or two, and dropping it, or by sitting in the seat and pushing down. It happens all the time and is beyond annoying. Trek has never heard of this problem, they say. Is this a problem with this shock or frame, or is this a normal noise. Thanks.