Recently installed a PS35 in my home. It is running as we speak and have questions concerning noises it makes. I hear a rumble that I am sure is air related. The rumble is intermittent and not just at start up. I hear the pellets as they fall down the shoot, but occasionally I hear what I would describe as a thud or maybe a crack. This takes place while feeding I think. Do I have some major problem or am I over thinking the whole deal. From what I have read here, the rumble sounds pretty common, but the other noise doesn't appear to have been addressed here or I just haven't looked hard enough.